Hi,

please backport the following commit[0] to all stable releases that contain the commit 226fae124b2d ("vc_screen: move load of struct vc_data pointer in vcs_read() to avoid UAF")

Commit 46d733d0efc7 ("vc_screen: modify vcs_size() handling in vcs_read()") [1] also tries to fix this commit but should not actually be necessary for a proper fix. It may make sense to also backport for consistency.

commit ae3419fbac845b4d3f3a9fae4cc80c68d82cdf6e Author: Thomas Weißschuh linux@weissschuh.net Date: Mon Feb 20 06:46:12 2023 +0000

vc_screen: don't clobber return value in vcs_read

Commit 226fae124b2d ("vc_screen: move load of struct vc_data pointer in vcs_read() to avoid UAF") moved the call to vcs_vc() into the loop.

While doing this it also moved the unconditional assignment of

ret = -ENXIO;

This unconditional assignment was valid outside the loop but within it it clobbers the actual value of ret.

To avoid this only assign "ret = -ENXIO" when actually needed.

[ Also, the 'goto unlock_out" needs to be just a "break", so that it does the right thing when it exits on later iterations when partial success has happened - Linus ]

Reported-by: Storm Dragon stormdragon2976@gmail.com Link: https://lore.kernel.org/lkml/Y%2FKS6vdql2pIsCiI@hotmail.com/ Fixes: 226fae124b2d ("vc_screen: move load of struct vc_data pointer in vcs_read() to avoid UAF") Signed-off-by: Thomas Weißschuh linux@weissschuh.net Link: https://lore.kernel.org/lkml/64981d94-d00c-4b31-9063-43ad0a384bde@t-8ch.de/ Signed-off-by: Linus Torvalds torvalds@linux-foundation.org

Thanks, Thomas

[0] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...