io_uring: enable audit and restrict cred override for IORING_OP_FIXED_FD_INSTALL
We need to correct some aspects of the IORING_OP_FIXED_FD_INSTALL
command to take into account the security implications of making an
io_uring-private file descriptor generally accessible to a userspace
task.
The first change in this patch is to enable auditing of the FD_INSTALL
operation as installing a file descriptor into a task's file descriptor
table is a security relevant operation and something that admins/users
may want to audit.
The second change is to disable the io_uring credential override
functionality, also known as io_uring "personalities", in the
FD_INSTALL command. The credential override in FD_INSTALL is
particularly problematic as it affects the credentials used in the
security_file_receive() LSM hook. If a task were to request a
credential override via REQ_F_CREDS on a FD_INSTALL operation, the LSM
would incorrectly check to see if the overridden credentials of the
io_uring were able to "receive" the file as opposed to the task's
credentials. After discussions upstream, it's difficult to imagine a
use case where we would want to allow a credential override on a
FD_INSTALL operation so we are simply going to block REQ_F_CREDS on
IORING_OP_FIXED_FD_INSTALL operations.
Fixes: dc18b89ab1
("io_uring/openclose: add support for IORING_OP_FIXED_FD_INSTALL")
Signed-off-by: Paul Moore <paul@paul-moore.com>
Link: https://lore.kernel.org/r/20240123215501.289566-2-paul@paul-moore.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
parent
6613476e22
commit
16bae3e137
io_uring
@ -471,7 +471,6 @@ const struct io_issue_def io_issue_defs[] = {
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},
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[IORING_OP_FIXED_FD_INSTALL] = {
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.needs_file = 1,
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.audit_skip = 1,
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.prep = io_install_fixed_fd_prep,
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.issue = io_install_fixed_fd,
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},
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@ -277,6 +277,10 @@ int io_install_fixed_fd_prep(struct io_kiocb *req, const struct io_uring_sqe *sq
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if (flags & ~IORING_FIXED_FD_NO_CLOEXEC)
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return -EINVAL;
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/* ensure the task's creds are used when installing/receiving fds */
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if (req->flags & REQ_F_CREDS)
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return -EPERM;
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/* default to O_CLOEXEC, disable if IORING_FIXED_FD_NO_CLOEXEC is set */
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ifi = io_kiocb_to_cmd(req, struct io_fixed_install);
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ifi->o_flags = O_CLOEXEC;
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