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authorPaul Moore <paul@paul-moore.com>2024-01-24 00:55:02 +0300
committerJens Axboe <axboe@kernel.dk>2024-01-24 01:25:14 +0300
commit16bae3e1377846734ec6b87eee459c0f3551692c (patch)
tree52972c02d261202cdf3676afdd00d00002f7dfa7 /io_uring
parent6613476e225e090cc9aad49be7fa504e290dd33d (diff)
downloadlinux-16bae3e1377846734ec6b87eee459c0f3551692c.tar.xz
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.c1
-rw-r--r--io_uring/openclose.c4
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;