From: Thomas Weißschuh linux@weissschuh.net
stable inclusion from stable-v5.10.171 commit 80653a6e6e287eb982be9aa9f60f94382b6767b5 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I7JRBO?from=project-issue
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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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@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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Lu Jialin lujialin4@huawei.com --- 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 f566eb1839dc..71e091f879f0 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