From ae3419fbac845b4d3f3a9fae4cc80c68d82cdf6e Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= Date: Mon, 20 Feb 2023 06:46:12 +0000 Subject: [PATCH] vc_screen: don't clobber return value in vcs_read MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 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 Link: https://lore.kernel.org/lkml/64981d94-d00c-4b31-9063-43ad0a384bde@t-8ch.de/ Signed-off-by: Linus Torvalds --- drivers/tty/vt/vc_screen.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/tty/vt/vc_screen.c b/drivers/tty/vt/vc_screen.c index c0a2273bb998..1dc07f9214d5 100644 --- a/drivers/tty/vt/vc_screen.c +++ b/drivers/tty/vt/vc_screen.c @@ -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