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| author | Jann Horn <jannh@google.com> | 2024-12-18 17:56:25 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-12-27 13:53:00 +0100 |
| commit | c034ce2668ae94f04ff46d29b195409614feaf75 (patch) | |
| tree | 802dc88077e12b02a0e1f4c6601218c5451f92be | |
| parent | 48d07e3a18cdde5d1a732a746e7e51c0e652aa06 (diff) | |
| download | linux-c034ce2668ae94f04ff46d29b195409614feaf75.tar.gz linux-c034ce2668ae94f04ff46d29b195409614feaf75.tar.bz2 linux-c034ce2668ae94f04ff46d29b195409614feaf75.zip | |
io_uring: Fix registered ring file refcount leak
commit 12d908116f7efd34f255a482b9afc729d7a5fb78 upstream.
Currently, io_uring_unreg_ringfd() (which cleans up registered rings) is
only called on exit, but __io_uring_free (which frees the tctx in which the
registered ring pointers are stored) is also called on execve (via
begin_new_exec -> io_uring_task_cancel -> __io_uring_cancel ->
io_uring_cancel_generic -> __io_uring_free).
This means: A process going through execve while having registered rings
will leak references to the rings' `struct file`.
Fix it by zapping registered rings on execve(). This is implemented by
moving the io_uring_unreg_ringfd() from io_uring_files_cancel() into its
callee __io_uring_cancel(), which is called from io_uring_task_cancel() on
execve.
This could probably be exploited *on 32-bit kernels* by leaking 2^32
references to the same ring, because the file refcount is stored in a
pointer-sized field and get_file() doesn't have protection against
refcount overflow, just a WARN_ONCE(); but on 64-bit it should have no
impact beyond a memory leak.
Cc: stable@vger.kernel.org
Fixes: e7a6c00dc77a ("io_uring: add support for registering ring file descriptors")
Signed-off-by: Jann Horn <jannh@google.com>
Link: https://lore.kernel.org/r/20241218-uring-reg-ring-cleanup-v1-1-8f63e999045b@google.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | include/linux/io_uring.h | 4 | ||||
| -rw-r--r-- | io_uring/io_uring.c | 1 |
2 files changed, 2 insertions, 3 deletions
diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h index a8f3058448ea..e0dec1bf917a 100644 --- a/include/linux/io_uring.h +++ b/include/linux/io_uring.h @@ -50,10 +50,8 @@ bool io_is_uring_fops(struct file *file); static inline void io_uring_files_cancel(void) { - if (current->io_uring) { - io_uring_unreg_ringfd(); + if (current->io_uring) __io_uring_cancel(false); - } } static inline void io_uring_task_cancel(void) { diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 0b1361663267..ae7a9545b877 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -3085,6 +3085,7 @@ __cold void io_uring_cancel_generic(bool cancel_all, struct io_sq_data *sqd) void __io_uring_cancel(bool cancel_all) { + io_uring_unreg_ringfd(); io_uring_cancel_generic(cancel_all, NULL); } |