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| author | Paul Moore <paul@paul-moore.com> | 2024-01-23 22:55:02 +0100 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2024-01-23 23:25:14 +0100 |
| commit | 16bae3e1377846734ec6b87eee459c0f3551692c (patch) | |
| tree | 52972c02d261202cdf3676afdd00d00002f7dfa7 /io_uring | |
| parent | Linux 6.8-rc1 (diff) | |
| download | linux-16bae3e1377846734ec6b87eee459c0f3551692c.tar.xz linux-16bae3e1377846734ec6b87eee459c0f3551692c.zip | |
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: dc18b89ab113 ("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>
Diffstat (limited to 'io_uring')
| -rw-r--r-- | io_uring/opdef.c | 1 | ||||
| -rw-r--r-- | io_uring/openclose.c | 4 |
2 files changed, 4 insertions, 1 deletions
diff --git a/io_uring/opdef.c b/io_uring/opdef.c index 6705634e5f52..b1ee3a9c3807 100644 --- a/io_uring/opdef.c +++ b/io_uring/opdef.c @@ -471,7 +471,6 @@ const struct io_issue_def io_issue_defs[] = { }, [IORING_OP_FIXED_FD_INSTALL] = { .needs_file = 1, - .audit_skip = 1, .prep = io_install_fixed_fd_prep, .issue = io_install_fixed_fd, }, diff --git a/io_uring/openclose.c b/io_uring/openclose.c index 0fe0dd305546..e3357dfa14ca 100644 --- a/io_uring/openclose.c +++ b/io_uring/openclose.c @@ -277,6 +277,10 @@ int io_install_fixed_fd_prep(struct io_kiocb *req, const struct io_uring_sqe *sq if (flags & ~IORING_FIXED_FD_NO_CLOEXEC) return -EINVAL; + /* ensure the task's creds are used when installing/receiving fds */ + if (req->flags & REQ_F_CREDS) + return -EPERM; + /* default to O_CLOEXEC, disable if IORING_FIXED_FD_NO_CLOEXEC is set */ ifi = io_kiocb_to_cmd(req, struct io_fixed_install); ifi->o_flags = O_CLOEXEC; |