1
linux/kernel/ptrace.c

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/*
* linux/kernel/ptrace.c
*
* (C) Copyright 1999 Linus Torvalds
*
* Common interfaces for "ptrace()" which we do not want
* to continually duplicate across every architecture.
*/
#include <linux/capability.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/smp_lock.h>
#include <linux/ptrace.h>
#include <linux/security.h>
#include <linux/signal.h>
#include <linux/audit.h>
#include <linux/pid_namespace.h>
#include <linux/syscalls.h>
#include <asm/pgtable.h>
#include <asm/uaccess.h>
/*
* ptrace a task: make the debugger its new parent and
* move it to the ptrace list.
*
* Must be called with the tasklist lock write-held.
*/
void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
{
BUG_ON(!list_empty(&child->ptrace_entry));
list_add(&child->ptrace_entry, &new_parent->ptraced);
child->parent = new_parent;
}
/*
* Turn a tracing stop into a normal stop now, since with no tracer there
* would be no way to wake it up with SIGCONT or SIGKILL. If there was a
* signal sent that would resume the child, but didn't because it was in
* TASK_TRACED, resume it now.
* Requires that irqs be disabled.
*/
static void ptrace_untrace(struct task_struct *child)
{
spin_lock(&child->sighand->siglock);
if (task_is_traced(child)) {
if (child->signal->flags & SIGNAL_STOP_STOPPED) {
__set_task_state(child, TASK_STOPPED);
} else {
signal_wake_up(child, 1);
}
}
spin_unlock(&child->sighand->siglock);
}
/*
* unptrace a task: move it back to its original parent and
* remove it from the ptrace list.
*
* Must be called with the tasklist lock write-held.
*/
void __ptrace_unlink(struct task_struct *child)
{
BUG_ON(!child->ptrace);
child->ptrace = 0;
child->parent = child->real_parent;
list_del_init(&child->ptrace_entry);
if (task_is_traced(child))
ptrace_untrace(child);
}
/*
* Check that we have indeed attached to the thing..
*/
int ptrace_check_attach(struct task_struct *child, int kill)
{
int ret = -ESRCH;
/*
* We take the read lock around doing both checks to close a
* possible race where someone else was tracing our child and
* detached between these two checks. After this locked check,
* we are sure that this is our traced child and that can only
* be changed by us so it's not changing right after this.
*/
read_lock(&tasklist_lock);
if ((child->ptrace & PT_PTRACED) && child->parent == current) {
ret = 0;
/*
* child->sighand can't be NULL, release_task()
* does ptrace_unlink() before __exit_signal().
*/
spin_lock_irq(&child->sighand->siglock);
if (task_is_stopped(child))
child->state = TASK_TRACED;
else if (!task_is_traced(child) && !kill)
ret = -ESRCH;
spin_unlock_irq(&child->sighand->siglock);
}
read_unlock(&tasklist_lock);
if (!ret && !kill)
ret = wait_task_inactive(child, TASK_TRACED) ? 0 : -ESRCH;
/* All systems go.. */
return ret;
}
Security: split proc ptrace checking into read vs. attach Enable security modules to distinguish reading of process state via proc from full ptrace access by renaming ptrace_may_attach to ptrace_may_access and adding a mode argument indicating whether only read access or full attach access is requested. This allows security modules to permit access to reading process state without granting full ptrace access. The base DAC/capability checking remains unchanged. Read access to /proc/pid/mem continues to apply a full ptrace attach check since check_mem_permission() already requires the current task to already be ptracing the target. The other ptrace checks within proc for elements like environ, maps, and fds are changed to pass the read mode instead of attach. In the SELinux case, we model such reading of process state as a reading of a proc file labeled with the target process' label. This enables SELinux policy to permit such reading of process state without permitting control or manipulation of the target process, as there are a number of cases where programs probe for such information via proc but do not need to be able to control the target (e.g. procps, lsof, PolicyKit, ConsoleKit). At present we have to choose between allowing full ptrace in policy (more permissive than required/desired) or breaking functionality (or in some cases just silencing the denials via dontaudit rules but this can hide genuine attacks). This version of the patch incorporates comments from Casey Schaufler (change/replace existing ptrace_may_attach interface, pass access mode), and Chris Wright (provide greater consistency in the checking). Note that like their predecessors __ptrace_may_attach and ptrace_may_attach, the __ptrace_may_access and ptrace_may_access interfaces use different return value conventions from each other (0 or -errno vs. 1 or 0). I retained this difference to avoid any changes to the caller logic but made the difference clearer by changing the latter interface to return a bool rather than an int and by adding a comment about it to ptrace.h for any future callers. Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> Acked-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: James Morris <jmorris@namei.org>
2008-05-19 05:32:49 -07:00
int __ptrace_may_access(struct task_struct *task, unsigned int mode)
{
/* May we inspect the given task?
* This check is used both for attaching with ptrace
* and for allowing access to sensitive information in /proc.
*
* ptrace_attach denies several cases that /proc allows
* because setting up the necessary parent/child relationship
* or halting the specified task is impossible.
*/
int dumpable = 0;
/* Don't let security modules deny introspection */
if (task == current)
return 0;
if (((current->uid != task->euid) ||
(current->uid != task->suid) ||
(current->uid != task->uid) ||
(current->gid != task->egid) ||
(current->gid != task->sgid) ||
(current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
return -EPERM;
smp_rmb();
if (task->mm)
dumpable = get_dumpable(task->mm);
if (!dumpable && !capable(CAP_SYS_PTRACE))
return -EPERM;
security: Fix setting of PF_SUPERPRIV by __capable() Fix the setting of PF_SUPERPRIV by __capable() as it could corrupt the flags the target process if that is not the current process and it is trying to change its own flags in a different way at the same time. __capable() is using neither atomic ops nor locking to protect t->flags. This patch removes __capable() and introduces has_capability() that doesn't set PF_SUPERPRIV on the process being queried. This patch further splits security_ptrace() in two: (1) security_ptrace_may_access(). This passes judgement on whether one process may access another only (PTRACE_MODE_ATTACH for ptrace() and PTRACE_MODE_READ for /proc), and takes a pointer to the child process. current is the parent. (2) security_ptrace_traceme(). This passes judgement on PTRACE_TRACEME only, and takes only a pointer to the parent process. current is the child. In Smack and commoncap, this uses has_capability() to determine whether the parent will be permitted to use PTRACE_ATTACH if normal checks fail. This does not set PF_SUPERPRIV. Two of the instances of __capable() actually only act on current, and so have been changed to calls to capable(). Of the places that were using __capable(): (1) The OOM killer calls __capable() thrice when weighing the killability of a process. All of these now use has_capability(). (2) cap_ptrace() and smack_ptrace() were using __capable() to check to see whether the parent was allowed to trace any process. As mentioned above, these have been split. For PTRACE_ATTACH and /proc, capable() is now used, and for PTRACE_TRACEME, has_capability() is used. (3) cap_safe_nice() only ever saw current, so now uses capable(). (4) smack_setprocattr() rejected accesses to tasks other than current just after calling __capable(), so the order of these two tests have been switched and capable() is used instead. (5) In smack_file_send_sigiotask(), we need to allow privileged processes to receive SIGIO on files they're manipulating. (6) In smack_task_wait(), we let a process wait for a privileged process, whether or not the process doing the waiting is privileged. I've tested this with the LTP SELinux and syscalls testscripts. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Serge Hallyn <serue@us.ibm.com> Acked-by: Casey Schaufler <casey@schaufler-ca.com> Acked-by: Andrew G. Morgan <morgan@kernel.org> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: James Morris <jmorris@namei.org>
2008-08-14 03:37:28 -07:00
return security_ptrace_may_access(task, mode);
}
Security: split proc ptrace checking into read vs. attach Enable security modules to distinguish reading of process state via proc from full ptrace access by renaming ptrace_may_attach to ptrace_may_access and adding a mode argument indicating whether only read access or full attach access is requested. This allows security modules to permit access to reading process state without granting full ptrace access. The base DAC/capability checking remains unchanged. Read access to /proc/pid/mem continues to apply a full ptrace attach check since check_mem_permission() already requires the current task to already be ptracing the target. The other ptrace checks within proc for elements like environ, maps, and fds are changed to pass the read mode instead of attach. In the SELinux case, we model such reading of process state as a reading of a proc file labeled with the target process' label. This enables SELinux policy to permit such reading of process state without permitting control or manipulation of the target process, as there are a number of cases where programs probe for such information via proc but do not need to be able to control the target (e.g. procps, lsof, PolicyKit, ConsoleKit). At present we have to choose between allowing full ptrace in policy (more permissive than required/desired) or breaking functionality (or in some cases just silencing the denials via dontaudit rules but this can hide genuine attacks). This version of the patch incorporates comments from Casey Schaufler (change/replace existing ptrace_may_attach interface, pass access mode), and Chris Wright (provide greater consistency in the checking). Note that like their predecessors __ptrace_may_attach and ptrace_may_attach, the __ptrace_may_access and ptrace_may_access interfaces use different return value conventions from each other (0 or -errno vs. 1 or 0). I retained this difference to avoid any changes to the caller logic but made the difference clearer by changing the latter interface to return a bool rather than an int and by adding a comment about it to ptrace.h for any future callers. Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> Acked-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: James Morris <jmorris@namei.org>
2008-05-19 05:32:49 -07:00
bool ptrace_may_access(struct task_struct *task, unsigned int mode)
{
int err;
task_lock(task);
Security: split proc ptrace checking into read vs. attach Enable security modules to distinguish reading of process state via proc from full ptrace access by renaming ptrace_may_attach to ptrace_may_access and adding a mode argument indicating whether only read access or full attach access is requested. This allows security modules to permit access to reading process state without granting full ptrace access. The base DAC/capability checking remains unchanged. Read access to /proc/pid/mem continues to apply a full ptrace attach check since check_mem_permission() already requires the current task to already be ptracing the target. The other ptrace checks within proc for elements like environ, maps, and fds are changed to pass the read mode instead of attach. In the SELinux case, we model such reading of process state as a reading of a proc file labeled with the target process' label. This enables SELinux policy to permit such reading of process state without permitting control or manipulation of the target process, as there are a number of cases where programs probe for such information via proc but do not need to be able to control the target (e.g. procps, lsof, PolicyKit, ConsoleKit). At present we have to choose between allowing full ptrace in policy (more permissive than required/desired) or breaking functionality (or in some cases just silencing the denials via dontaudit rules but this can hide genuine attacks). This version of the patch incorporates comments from Casey Schaufler (change/replace existing ptrace_may_attach interface, pass access mode), and Chris Wright (provide greater consistency in the checking). Note that like their predecessors __ptrace_may_attach and ptrace_may_attach, the __ptrace_may_access and ptrace_may_access interfaces use different return value conventions from each other (0 or -errno vs. 1 or 0). I retained this difference to avoid any changes to the caller logic but made the difference clearer by changing the latter interface to return a bool rather than an int and by adding a comment about it to ptrace.h for any future callers. Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> Acked-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: James Morris <jmorris@namei.org>
2008-05-19 05:32:49 -07:00
err = __ptrace_may_access(task, mode);
task_unlock(task);
Security: split proc ptrace checking into read vs. attach Enable security modules to distinguish reading of process state via proc from full ptrace access by renaming ptrace_may_attach to ptrace_may_access and adding a mode argument indicating whether only read access or full attach access is requested. This allows security modules to permit access to reading process state without granting full ptrace access. The base DAC/capability checking remains unchanged. Read access to /proc/pid/mem continues to apply a full ptrace attach check since check_mem_permission() already requires the current task to already be ptracing the target. The other ptrace checks within proc for elements like environ, maps, and fds are changed to pass the read mode instead of attach. In the SELinux case, we model such reading of process state as a reading of a proc file labeled with the target process' label. This enables SELinux policy to permit such reading of process state without permitting control or manipulation of the target process, as there are a number of cases where programs probe for such information via proc but do not need to be able to control the target (e.g. procps, lsof, PolicyKit, ConsoleKit). At present we have to choose between allowing full ptrace in policy (more permissive than required/desired) or breaking functionality (or in some cases just silencing the denials via dontaudit rules but this can hide genuine attacks). This version of the patch incorporates comments from Casey Schaufler (change/replace existing ptrace_may_attach interface, pass access mode), and Chris Wright (provide greater consistency in the checking). Note that like their predecessors __ptrace_may_attach and ptrace_may_attach, the __ptrace_may_access and ptrace_may_access interfaces use different return value conventions from each other (0 or -errno vs. 1 or 0). I retained this difference to avoid any changes to the caller logic but made the difference clearer by changing the latter interface to return a bool rather than an int and by adding a comment about it to ptrace.h for any future callers. Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> Acked-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: James Morris <jmorris@namei.org>
2008-05-19 05:32:49 -07:00
return (!err ? true : false);
}
int ptrace_attach(struct task_struct *task)
{
int retval;
unsigned long flags;
audit_ptrace(task);
retval = -EPERM;
if (same_thread_group(task, current))
goto out;
repeat:
/*
* Nasty, nasty.
*
* We want to hold both the task-lock and the
* tasklist_lock for writing at the same time.
* But that's against the rules (tasklist_lock
* is taken for reading by interrupts on other
* cpu's that may have task_lock).
*/
task_lock(task);
if (!write_trylock_irqsave(&tasklist_lock, flags)) {
task_unlock(task);
do {
cpu_relax();
} while (!write_can_lock(&tasklist_lock));
goto repeat;
}
if (!task->mm)
goto bad;
/* the same process cannot be attached many times */
if (task->ptrace & PT_PTRACED)
goto bad;
Security: split proc ptrace checking into read vs. attach Enable security modules to distinguish reading of process state via proc from full ptrace access by renaming ptrace_may_attach to ptrace_may_access and adding a mode argument indicating whether only read access or full attach access is requested. This allows security modules to permit access to reading process state without granting full ptrace access. The base DAC/capability checking remains unchanged. Read access to /proc/pid/mem continues to apply a full ptrace attach check since check_mem_permission() already requires the current task to already be ptracing the target. The other ptrace checks within proc for elements like environ, maps, and fds are changed to pass the read mode instead of attach. In the SELinux case, we model such reading of process state as a reading of a proc file labeled with the target process' label. This enables SELinux policy to permit such reading of process state without permitting control or manipulation of the target process, as there are a number of cases where programs probe for such information via proc but do not need to be able to control the target (e.g. procps, lsof, PolicyKit, ConsoleKit). At present we have to choose between allowing full ptrace in policy (more permissive than required/desired) or breaking functionality (or in some cases just silencing the denials via dontaudit rules but this can hide genuine attacks). This version of the patch incorporates comments from Casey Schaufler (change/replace existing ptrace_may_attach interface, pass access mode), and Chris Wright (provide greater consistency in the checking). Note that like their predecessors __ptrace_may_attach and ptrace_may_attach, the __ptrace_may_access and ptrace_may_access interfaces use different return value conventions from each other (0 or -errno vs. 1 or 0). I retained this difference to avoid any changes to the caller logic but made the difference clearer by changing the latter interface to return a bool rather than an int and by adding a comment about it to ptrace.h for any future callers. Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov> Acked-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: James Morris <jmorris@namei.org>
2008-05-19 05:32:49 -07:00
retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
if (retval)
goto bad;
/* Go */
task->ptrace |= PT_PTRACED;
if (capable(CAP_SYS_PTRACE))
task->ptrace |= PT_PTRACE_CAP;
__ptrace_link(task, current);
send_sig_info(SIGSTOP, SEND_SIG_FORCED, task);
bad:
write_unlock_irqrestore(&tasklist_lock, flags);
task_unlock(task);
out:
return retval;
}
static inline void __ptrace_detach(struct task_struct *child, unsigned int data)
{
child->exit_code = data;
/* .. re-parent .. */
__ptrace_unlink(child);
/* .. and wake it up. */
if (child->exit_state != EXIT_ZOMBIE)
wake_up_process(child);
}
int ptrace_detach(struct task_struct *child, unsigned int data)
{
if (!valid_signal(data))
return -EIO;
/* Architecture-specific hardware disable .. */
ptrace_disable(child);
clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
write_lock_irq(&tasklist_lock);
/* protect against de_thread()->release_task() */
if (child->ptrace)
__ptrace_detach(child, data);
write_unlock_irq(&tasklist_lock);
return 0;
}
int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
{
int copied = 0;
while (len > 0) {
char buf[128];
int this_len, retval;
this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
retval = access_process_vm(tsk, src, buf, this_len, 0);
if (!retval) {
if (copied)
break;
return -EIO;
}
if (copy_to_user(dst, buf, retval))
return -EFAULT;
copied += retval;
src += retval;
dst += retval;
len -= retval;
}
return copied;
}
int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len)
{
int copied = 0;
while (len > 0) {
char buf[128];
int this_len, retval;
this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
if (copy_from_user(buf, src, this_len))
return -EFAULT;
retval = access_process_vm(tsk, dst, buf, this_len, 1);
if (!retval) {
if (copied)
break;
return -EIO;
}
copied += retval;
src += retval;
dst += retval;
len -= retval;
}
return copied;
}
static int ptrace_setoptions(struct task_struct *child, long data)
{
child->ptrace &= ~PT_TRACE_MASK;
if (data & PTRACE_O_TRACESYSGOOD)
child->ptrace |= PT_TRACESYSGOOD;
if (data & PTRACE_O_TRACEFORK)
child->ptrace |= PT_TRACE_FORK;
if (data & PTRACE_O_TRACEVFORK)
child->ptrace |= PT_TRACE_VFORK;
if (data & PTRACE_O_TRACECLONE)
child->ptrace |= PT_TRACE_CLONE;
if (data & PTRACE_O_TRACEEXEC)
child->ptrace |= PT_TRACE_EXEC;
if (data & PTRACE_O_TRACEVFORKDONE)
child->ptrace |= PT_TRACE_VFORK_DONE;
if (data & PTRACE_O_TRACEEXIT)
child->ptrace |= PT_TRACE_EXIT;
return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
}
static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
{
int error = -ESRCH;
read_lock(&tasklist_lock);
if (likely(child->sighand != NULL)) {
error = -EINVAL;
spin_lock_irq(&child->sighand->siglock);
if (likely(child->last_siginfo != NULL)) {
*info = *child->last_siginfo;
error = 0;
}
spin_unlock_irq(&child->sighand->siglock);
}
read_unlock(&tasklist_lock);
return error;
}
static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
{
int error = -ESRCH;
read_lock(&tasklist_lock);
if (likely(child->sighand != NULL)) {
error = -EINVAL;
spin_lock_irq(&child->sighand->siglock);
if (likely(child->last_siginfo != NULL)) {
*child->last_siginfo = *info;
error = 0;
}
spin_unlock_irq(&child->sighand->siglock);
}
read_unlock(&tasklist_lock);
return error;
}
#ifdef PTRACE_SINGLESTEP
#define is_singlestep(request) ((request) == PTRACE_SINGLESTEP)
#else
#define is_singlestep(request) 0
#endif
#ifdef PTRACE_SINGLEBLOCK
#define is_singleblock(request) ((request) == PTRACE_SINGLEBLOCK)
#else
#define is_singleblock(request) 0
#endif
#ifdef PTRACE_SYSEMU
#define is_sysemu_singlestep(request) ((request) == PTRACE_SYSEMU_SINGLESTEP)
#else
#define is_sysemu_singlestep(request) 0
#endif
static int ptrace_resume(struct task_struct *child, long request, long data)
{
if (!valid_signal(data))
return -EIO;
if (request == PTRACE_SYSCALL)
set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
else
clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
#ifdef TIF_SYSCALL_EMU
if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)
set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
else
clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
#endif
if (is_singleblock(request)) {
if (unlikely(!arch_has_block_step()))
return -EIO;
user_enable_block_step(child);
} else if (is_singlestep(request) || is_sysemu_singlestep(request)) {
if (unlikely(!arch_has_single_step()))
return -EIO;
user_enable_single_step(child);
}
else
user_disable_single_step(child);
child->exit_code = data;
wake_up_process(child);
return 0;
}
int ptrace_request(struct task_struct *child, long request,
long addr, long data)
{
int ret = -EIO;
siginfo_t siginfo;
switch (request) {
case PTRACE_PEEKTEXT:
case PTRACE_PEEKDATA:
return generic_ptrace_peekdata(child, addr, data);
case PTRACE_POKETEXT:
case PTRACE_POKEDATA:
return generic_ptrace_pokedata(child, addr, data);
#ifdef PTRACE_OLDSETOPTIONS
case PTRACE_OLDSETOPTIONS:
#endif
case PTRACE_SETOPTIONS:
ret = ptrace_setoptions(child, data);
break;
case PTRACE_GETEVENTMSG:
ret = put_user(child->ptrace_message, (unsigned long __user *) data);
break;
case PTRACE_GETSIGINFO:
ret = ptrace_getsiginfo(child, &siginfo);
if (!ret)
ret = copy_siginfo_to_user((siginfo_t __user *) data,
&siginfo);
break;
case PTRACE_SETSIGINFO:
if (copy_from_user(&siginfo, (siginfo_t __user *) data,
sizeof siginfo))
ret = -EFAULT;
else
ret = ptrace_setsiginfo(child, &siginfo);
break;
case PTRACE_DETACH: /* detach a process that was attached. */
ret = ptrace_detach(child, data);
break;
#ifdef PTRACE_SINGLESTEP
case PTRACE_SINGLESTEP:
#endif
#ifdef PTRACE_SINGLEBLOCK
case PTRACE_SINGLEBLOCK:
#endif
#ifdef PTRACE_SYSEMU
case PTRACE_SYSEMU:
case PTRACE_SYSEMU_SINGLESTEP:
#endif
case PTRACE_SYSCALL:
case PTRACE_CONT:
return ptrace_resume(child, request, data);
case PTRACE_KILL:
if (child->exit_state) /* already dead */
return 0;
return ptrace_resume(child, request, SIGKILL);
default:
break;
}
return ret;
}
/**
* ptrace_traceme -- helper for PTRACE_TRACEME
*
* Performs checks and sets PT_PTRACED.
* Should be used by all ptrace implementations for PTRACE_TRACEME.
*/
int ptrace_traceme(void)
{
int ret = -EPERM;
/*
* Are we already being traced?
*/
repeat:
task_lock(current);
if (!(current->ptrace & PT_PTRACED)) {
/*
* See ptrace_attach() comments about the locking here.
*/
unsigned long flags;
if (!write_trylock_irqsave(&tasklist_lock, flags)) {
task_unlock(current);
do {
cpu_relax();
} while (!write_can_lock(&tasklist_lock));
goto repeat;
}
security: Fix setting of PF_SUPERPRIV by __capable() Fix the setting of PF_SUPERPRIV by __capable() as it could corrupt the flags the target process if that is not the current process and it is trying to change its own flags in a different way at the same time. __capable() is using neither atomic ops nor locking to protect t->flags. This patch removes __capable() and introduces has_capability() that doesn't set PF_SUPERPRIV on the process being queried. This patch further splits security_ptrace() in two: (1) security_ptrace_may_access(). This passes judgement on whether one process may access another only (PTRACE_MODE_ATTACH for ptrace() and PTRACE_MODE_READ for /proc), and takes a pointer to the child process. current is the parent. (2) security_ptrace_traceme(). This passes judgement on PTRACE_TRACEME only, and takes only a pointer to the parent process. current is the child. In Smack and commoncap, this uses has_capability() to determine whether the parent will be permitted to use PTRACE_ATTACH if normal checks fail. This does not set PF_SUPERPRIV. Two of the instances of __capable() actually only act on current, and so have been changed to calls to capable(). Of the places that were using __capable(): (1) The OOM killer calls __capable() thrice when weighing the killability of a process. All of these now use has_capability(). (2) cap_ptrace() and smack_ptrace() were using __capable() to check to see whether the parent was allowed to trace any process. As mentioned above, these have been split. For PTRACE_ATTACH and /proc, capable() is now used, and for PTRACE_TRACEME, has_capability() is used. (3) cap_safe_nice() only ever saw current, so now uses capable(). (4) smack_setprocattr() rejected accesses to tasks other than current just after calling __capable(), so the order of these two tests have been switched and capable() is used instead. (5) In smack_file_send_sigiotask(), we need to allow privileged processes to receive SIGIO on files they're manipulating. (6) In smack_task_wait(), we let a process wait for a privileged process, whether or not the process doing the waiting is privileged. I've tested this with the LTP SELinux and syscalls testscripts. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Serge Hallyn <serue@us.ibm.com> Acked-by: Casey Schaufler <casey@schaufler-ca.com> Acked-by: Andrew G. Morgan <morgan@kernel.org> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: James Morris <jmorris@namei.org>
2008-08-14 03:37:28 -07:00
ret = security_ptrace_traceme(current->parent);
/*
* Set the ptrace bit in the process ptrace flags.
* Then link us on our parent's ptraced list.
*/
if (!ret) {
current->ptrace |= PT_PTRACED;
__ptrace_link(current, current->real_parent);
}
write_unlock_irqrestore(&tasklist_lock, flags);
}
task_unlock(current);
return ret;
}
/**
* ptrace_get_task_struct -- grab a task struct reference for ptrace
* @pid: process id to grab a task_struct reference of
*
* This function is a helper for ptrace implementations. It checks
* permissions and then grabs a task struct for use of the actual
* ptrace implementation.
*
* Returns the task_struct for @pid or an ERR_PTR() on failure.
*/
struct task_struct *ptrace_get_task_struct(pid_t pid)
{
struct task_struct *child;
read_lock(&tasklist_lock);
child = find_task_by_vpid(pid);
if (child)
get_task_struct(child);
read_unlock(&tasklist_lock);
if (!child)
return ERR_PTR(-ESRCH);
return child;
}
#ifndef arch_ptrace_attach
#define arch_ptrace_attach(child) do { } while (0)
#endif
asmlinkage long sys_ptrace(long request, long pid, long addr, long data)
{
struct task_struct *child;
long ret;
/*
* This lock_kernel fixes a subtle race with suid exec
*/
lock_kernel();
if (request == PTRACE_TRACEME) {
ret = ptrace_traceme();
if (!ret)
arch_ptrace_attach(current);
goto out;
}
child = ptrace_get_task_struct(pid);
if (IS_ERR(child)) {
ret = PTR_ERR(child);
goto out;
}
if (request == PTRACE_ATTACH) {
ret = ptrace_attach(child);
/*
* Some architectures need to do book-keeping after
* a ptrace attach.
*/
if (!ret)
arch_ptrace_attach(child);
goto out_put_task_struct;
}
ret = ptrace_check_attach(child, request == PTRACE_KILL);
if (ret < 0)
goto out_put_task_struct;
ret = arch_ptrace(child, request, addr, data);
if (ret < 0)
goto out_put_task_struct;
out_put_task_struct:
put_task_struct(child);
out:
unlock_kernel();
return ret;
}
int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data)
{
unsigned long tmp;
int copied;
copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0);
if (copied != sizeof(tmp))
return -EIO;
return put_user(tmp, (unsigned long __user *)data);
}
int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data)
{
int copied;
copied = access_process_vm(tsk, addr, &data, sizeof(data), 1);
return (copied == sizeof(data)) ? 0 : -EIO;
}
#if defined CONFIG_COMPAT && defined __ARCH_WANT_COMPAT_SYS_PTRACE
#include <linux/compat.h>
int compat_ptrace_request(struct task_struct *child, compat_long_t request,
compat_ulong_t addr, compat_ulong_t data)
{
compat_ulong_t __user *datap = compat_ptr(data);
compat_ulong_t word;
siginfo_t siginfo;
int ret;
switch (request) {
case PTRACE_PEEKTEXT:
case PTRACE_PEEKDATA:
ret = access_process_vm(child, addr, &word, sizeof(word), 0);
if (ret != sizeof(word))
ret = -EIO;
else
ret = put_user(word, datap);
break;
case PTRACE_POKETEXT:
case PTRACE_POKEDATA:
ret = access_process_vm(child, addr, &data, sizeof(data), 1);
ret = (ret != sizeof(data) ? -EIO : 0);
break;
case PTRACE_GETEVENTMSG:
ret = put_user((compat_ulong_t) child->ptrace_message, datap);
break;
case PTRACE_GETSIGINFO:
ret = ptrace_getsiginfo(child, &siginfo);
if (!ret)
ret = copy_siginfo_to_user32(
(struct compat_siginfo __user *) datap,
&siginfo);
break;
case PTRACE_SETSIGINFO:
memset(&siginfo, 0, sizeof siginfo);
if (copy_siginfo_from_user32(
&siginfo, (struct compat_siginfo __user *) datap))
ret = -EFAULT;
else
ret = ptrace_setsiginfo(child, &siginfo);
break;
default:
ret = ptrace_request(child, request, addr, data);
}
return ret;
}
asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid,
compat_long_t addr, compat_long_t data)
{
struct task_struct *child;
long ret;
/*
* This lock_kernel fixes a subtle race with suid exec
*/
lock_kernel();
if (request == PTRACE_TRACEME) {
ret = ptrace_traceme();
goto out;
}
child = ptrace_get_task_struct(pid);
if (IS_ERR(child)) {
ret = PTR_ERR(child);
goto out;
}
if (request == PTRACE_ATTACH) {
ret = ptrace_attach(child);
/*
* Some architectures need to do book-keeping after
* a ptrace attach.
*/
if (!ret)
arch_ptrace_attach(child);
goto out_put_task_struct;
}
ret = ptrace_check_attach(child, request == PTRACE_KILL);
if (!ret)
ret = compat_arch_ptrace(child, request, addr, data);
out_put_task_struct:
put_task_struct(child);
out:
unlock_kernel();
return ret;
}
#endif /* CONFIG_COMPAT && __ARCH_WANT_COMPAT_SYS_PTRACE */