Unverified Commit a260bd22 authored by Mathias Krause's avatar Mathias Krause Committed by Christian Brauner
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media: mc: fix potential use-after-free in media_request_alloc() 



Commit 6f504cbf ("media: convert media_request_alloc() to
FD_PREPARE()") moved the call to fd_install() (now hidden in
fd_publish()) before the snprintf(), making the later write to
potentially already freed memory, as userland is free to call
close() concurrently right after the call to fd_install() which
may end up in the request_fops.release() handler freeing 'req'.

Fixes: 6f504cbf ("media: convert media_request_alloc() to FD_PREPARE()")
Signed-off-by: default avatarMathias Krause <minipli@grsecurity.net>
Link: https://patch.msgid.link/20251209210903.603958-1-minipli@grsecurity.net


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 8f0b4cce

drivers/media/mc/mc-request.c

+3 −3
Original line number Diff line number Diff line
@@ -315,12 +315,12 @@ int media_request_alloc(struct media_device *mdev, int *alloc_fd) 


	fd_prepare_file(fdf)->private_data = req;



	*alloc_fd = fd_publish(fdf);



	snprintf(req->debug_str, sizeof(req->debug_str), "%u:%d",

		 atomic_inc_return(&mdev->request_id), *alloc_fd);

		 atomic_inc_return(&mdev->request_id), fd_prepare_fd(fdf));

	dev_dbg(mdev->dev, "request: allocated %s\n", req->debug_str);



	*alloc_fd = fd_publish(fdf);



	return 0;



err_free_req: