This is a note to let you know that I've just added the patch titled
vc_screen: don't clobber return value in vcs_read
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
vc_screen-don-t-clobber-return-value-in-vcs_read.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ae3419fbac845b4d3f3a9fae4cc80c68d82cdf6e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= <linux@xxxxxxxxxxxxxx>
Date: Mon, 20 Feb 2023 06:46:12 +0000
Subject: vc_screen: don't clobber return value in vcs_read
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From: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
commit ae3419fbac845b4d3f3a9fae4cc80c68d82cdf6e upstream.
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@xxxxxxxxx>
Link: https://lore.kernel.org/lkml/Y%2FKS6vdql2pIsCiI@xxxxxxxxxxx/
Fixes: 226fae124b2d ("vc_screen: move load of struct vc_data pointer in vcs_read() to avoid UAF")
Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/lkml/64981d94-d00c-4b31-9063-43ad0a384bde@xxxxxxxx/
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/vt/vc_screen.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
--- a/drivers/tty/vt/vc_screen.c
+++ b/drivers/tty/vt/vc_screen.c
@@ -284,10 +284,11 @@ vcs_read(struct file *file, char __user
ssize_t orig_count;
long p = pos;
- 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
Patches currently in stable-queue which might be from linux@xxxxxxxxxxxxxx are
queue-5.4/vc_screen-don-t-clobber-return-value-in-vcs_read.patch
