Commit ae3419fb authored by Thomas Weißschuh's avatar Thomas Weißschuh Committed by Linus Torvalds
Browse files

vc_screen: don't clobber return value in vcs_read 



Commit 226fae12 ("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: default avatarStorm Dragon <stormdragon2976@gmail.com>
Link: https://lore.kernel.org/lkml/Y%2FKS6vdql2pIsCiI@hotmail.com/


Fixes: 226fae12 ("vc_screen: move load of struct vc_data pointer in vcs_read() to avoid UAF")
Signed-off-by: default avatarThomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/lkml/64981d94-d00c-4b31-9063-43ad0a384bde@t-8ch.de/


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 981ee95c

drivers/tty/vt/vc_screen.c

+4 −3
Original line number Diff line number Diff line
@@ -403,10 +403,11 @@ vcs_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) 
		unsigned int this_round, skip = 0;

		int size;



		ret = -ENXIO;

		vc = vcs_vc(inode, &viewed);

		if (!vc)

			goto unlock_out;

		if (!vc) {

			ret = -ENXIO;

			break;

		}



		/* Check whether we are above size each round,

		 * as copy_to_user at the end of this loop