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778c114477
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Eric W. Biederman 778c114477 [PATCH] proc: Use sane permission checks on the /proc/<pid>/fd/ symlinks 
Since 2.2 we have been doing a chroot check to see if it is appropriate to
return a read or follow one of these magic symlinks.  The chroot check was
asking a question about the visibility of files to the calling process and
it was actually checking the destination process, and not the files
themselves.  That test was clearly bogus.

In my first pass through I simply fixed the test to check the visibility of
the files themselves.  That naive approach to fixing the permissions was
too strict and resulted in cases where a task could not even see all of
it's file descriptors.

What has disturbed me about relaxing this check is that file descriptors
are per-process private things, and they are occasionaly used a user space
capability tokens.  Looking a little farther into the symlink path on /proc
I did find userid checks and a check for capability (CAP_DAC_OVERRIDE) so
there were permissions checking this.

But I was still concerned about privacy.  Besides /proc there is only one
other way to find out this kind of information, and that is ptrace.  ptrace
has been around for a long time and it has a well established security
model.

So after thinking about it I finally realized that the permission checks
that make sense are the permission checks applied to ptrace_attach.  The
checks are simple per process, and won't cause nasty surprises for people
coming from less capable unices.

Unfortunately there is one case that the current ptrace_attach test does
not cover: Zombies and kernel threads.  Single stepping those kinds of
processes is impossible.  Being able to see which file descriptors are open
on these tasks is important to lsof, fuser and friends.  So for these
special processes I made the rule you can't find out unless you have
CAP_SYS_PTRACE.

These proc permission checks should now conform to the principle of least
surprise.  As well as using much less code to implement :)

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-26 09:58:26 -07:00
..
9p Merge git://git.linux-nfs.org/pub/linux/nfs-2.6 2006-06-25 10:54:14 -07:00
adfs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
affs [PATCH] fix %s in affs_fill_super() 2006-06-25 10:01:22 -07:00
afs [PATCH] fs: use list_move() 2006-06-26 09:58:18 -07:00
autofs [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
autofs4 [PATCH] fs: use list_move() 2006-06-26 09:58:18 -07:00
befs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
bfs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
cifs Merge branch 'master' of /home/trondmy/kernel/linux-2.6/ 2006-06-24 13:07:53 -04:00
coda [PATCH] use list_add_tail() instead of list_add() 2006-06-26 09:58:17 -07:00
configfs [PATCH] fs: use list_move() 2006-06-26 09:58:18 -07:00
cramfs [PATCH] read_mapping_page for address space 2006-06-23 07:43:02 -07:00
debugfs Merge branch 'master' of /home/trondmy/kernel/linux-2.6/ 2006-06-24 13:07:53 -04:00
devfs [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
devpts [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
efs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
exportfs [PATCH] NFS server subtree_check returns dubious value 2006-05-21 12:59:16 -07:00
ext2 [PATCH] ext2: cleanup: put_page and comment fix 2006-06-25 10:01:25 -07:00
ext3 [PATCH] ext3: Add "-o bh" option 2006-06-26 09:58:20 -07:00
fat [PATCH] fs/fat/misc.c: unexport fat_sync_bhs 2006-06-23 07:43:03 -07:00
freevxfs [PATCH] fs/freevxfs: cleanup of spelling errors 2006-06-25 10:01:01 -07:00
fuse Merge git://git.linux-nfs.org/pub/linux/nfs-2.6 2006-06-25 10:54:14 -07:00
hfs [PATCH] read_mapping_page for address space 2006-06-23 07:43:02 -07:00
hfsplus [PATCH] read_mapping_page for address space 2006-06-23 07:43:02 -07:00
hostfs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
hpfs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
hppfs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
hugetlbfs [PATCH] tightening hugetlb strict accounting 2006-06-23 07:42:48 -07:00
isofs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
jbd [PATCH] ext3: fix memory leak when the journal file is corrupted 2006-06-25 10:01:07 -07:00
jffs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
jffs2 [PATCH] fs: use list_move() 2006-06-26 09:58:18 -07:00
jfs [PATCH] read_mapping_page for address space 2006-06-23 07:43:02 -07:00
lockd NLM: Fix reclaim races 2006-06-09 09:40:27 -04:00
minix [PATCH] read_mapping_page for address space 2006-06-23 07:43:02 -07:00
msdos [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
ncpfs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
nfs Fix NFS2 compile error 2006-06-25 12:30:33 -07:00
nfs_common
nfsd [PATCH] fs: use list_move() 2006-06-26 09:58:18 -07:00
nls
ntfs [PATCH] Prepare for __copy_from_user_inatomic to not zero missed bytes 2006-06-25 10:01:09 -07:00
ocfs2 [PATCH] fs: use list_move() 2006-06-26 09:58:18 -07:00
openpromfs [PATCH] openpromfs: factorize out 2006-06-25 10:01:05 -07:00
partitions [PATCH] make kernel warn about incorrectly sized partitions 2006-06-23 07:43:09 -07:00
proc [PATCH] proc: Use sane permission checks on the /proc/<pid>/fd/ symlinks 2006-06-26 09:58:26 -07:00
qnx4 [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
ramfs [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
reiserfs [PATCH] reiserfs: remove reiserfs_aio_write() 2006-06-26 09:58:19 -07:00
romfs [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
smbfs [PATCH] fs: use list_move() 2006-06-26 09:58:18 -07:00
sysfs [PATCH] core: use list_move() 2006-06-26 09:58:17 -07:00
sysv [PATCH] read_mapping_page for address space 2006-06-23 07:43:02 -07:00
udf [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
ufs [PATCH] fs/ufs/inode.c: make 2 functions static 2006-06-25 10:01:04 -07:00
vfat [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
xfs [PATCH] xfs: update ->flush method proto 2006-06-25 17:43:32 -07:00
aio.c [PATCH] list: use list_replace_init() instead of list_splice_init() 2006-06-23 07:43:07 -07:00
attr.c
bad_inode.c
binfmt_aout.c
binfmt_elf_fdpic.c [PATCH] frv: binfmt_elf_fdpic __user annotations 2006-06-23 07:42:54 -07:00
binfmt_elf.c [PATCH] binflt_elf: remove more casts 2006-06-23 07:43:05 -07:00
binfmt_em86.c
binfmt_flat.c [PATCH] uclinux: use PER_LINUX_32BIT in binfmt_flat 2006-06-25 21:04:24 -07:00
binfmt_misc.c Merge branch 'master' of /home/trondmy/kernel/linux-2.6/ 2006-06-24 13:07:53 -04:00
binfmt_script.c
binfmt_som.c
bio.c [PATCH] Fix missing ret assignment in __bio_map_user() error path 2006-06-17 10:52:12 -07:00
block_dev.c [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
buffer.c [PATCH] Kill PF_SYNCWRITE flag 2006-06-23 17:10:39 +02:00
char_dev.c
compat_ioctl.c [PATCH] i4l: Gigaset drivers: add IOCTLs to compat_ioctl.h 2006-06-26 09:58:23 -07:00
compat.c [PATCH] VFS: Permit filesystem to perform statfs with a known root dentry 2006-06-23 07:42:45 -07:00
dcache.c [PATCH] core: use list_move() 2006-06-26 09:58:17 -07:00
dcookies.c
direct-io.c [PATCH] Kill PF_SYNCWRITE flag 2006-06-23 17:10:39 +02:00
dnotify.c
dquot.c [PATCH] use list_add_tail() instead of list_add() 2006-06-26 09:58:17 -07:00
drop_caches.c
eventpoll.c [PATCH] epoll: use unlocked wqueue operations 2006-06-25 10:01:13 -07:00
exec.c [PATCH] proc: Rewrite the proc dentry flush on exit optimization 2006-06-26 09:58:24 -07:00
fcntl.c
fifo.c
file_table.c [PATCH] percpu counter data type changes to suppport more than 2**31 ext3 free blocks counter 2006-06-23 07:43:06 -07:00
file.c
filesystems.c
fs-writeback.c [PATCH] Kill PF_SYNCWRITE flag 2006-06-23 17:10:39 +02:00
inode.c
inotify_user.c [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
inotify.c [PATCH] inotify (4/5): allow watch removal from event handler 2006-06-20 05:25:19 -04:00
ioctl.c
ioprio.c [PATCH] lsm: add task_setioprio hook 2006-06-23 07:42:53 -07:00
Kconfig [PATCH] nfsd kconfig: select things at the closest tristate instead of bool 2006-06-26 09:58:23 -07:00
Kconfig.binfmt
libfs.c [PATCH] core: use list_move() 2006-06-26 09:58:17 -07:00
locks.c [PATCH] fs/locks.c: make posix_locks_deadlock() static 2006-06-23 07:43:03 -07:00
Makefile [PATCH] inotify (1/5): split kernel API from userspace support 2006-06-20 05:25:17 -04:00
mbcache.c
mpage.c [PATCH] writeback: fix range handling 2006-06-23 07:42:49 -07:00
namei.c [PATCH] Implement AT_SYMLINK_FOLLOW flag for linkat 2006-06-25 10:01:22 -07:00
namespace.c [PATCH] core: use list_move() 2006-06-26 09:58:17 -07:00
nfsctl.c
open.c [PATCH] ftruncate does not always update m/ctime 2006-06-25 10:01:15 -07:00
pipe.c [PATCH] VFS: Permit filesystem to override root dentry on mount 2006-06-23 07:42:45 -07:00
pnode.c [PATCH] core: use list_move() 2006-06-26 09:58:17 -07:00
pnode.h
posix_acl.c
quota_v1.c
quota_v2.c
quota.c
read_write.c
readdir.c
select.c [PATCH] fs: sys_poll with timeout -1 bug fix 2006-06-25 10:01:22 -07:00
seq_file.c
splice.c [PATCH] splice: retrieve mapping after locking the page 2006-06-23 17:10:39 +02:00
stat.c [PATCH] powerpc: Wire up *at syscalls 2006-04-28 21:04:59 +10:00
super.c Merge branch 'master' of /home/trondmy/kernel/linux-2.6/ 2006-06-24 13:07:53 -04:00
sync.c [PATCH] writeback: fix range handling 2006-06-23 07:42:49 -07:00
xattr_acl.c
xattr.c [PATCH] log more info for directory entry change events 2006-06-20 05:25:28 -04:00