Messages in this thread | | | Date | Tue, 21 Feb 2023 08:30:11 -0500 | Subject | Re: [PATCH] vc_screen: don't clobber return value in vcs_read | From | George Kennedy <> |
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On 2/20/2023 11:34 AM, Thomas Weißschuh wrote: > +Cc people who were involved in the original thread. > > On Mon, Feb 20, 2023 at 12:48:59PM +0100, Jiri Slaby wrote: >> On 20. 02. 23, 7:46, linux@weissschuh.net wrote: >>> From: Thomas Weißschuh <linux@weissschuh.net> >>> >>> 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. >> Not sure -- I cannot find it -- but hasn't George fixed this yet? > Indeed there was a proposed fix at > https://lore.kernel.org/lkml/1675704844-17228-1-git-send-email-george.kennedy@oracle.com/ > > Linus had some suggestions so it was not applied as is. > > I'm not sure what the current state is. > George, do you have something in the pipeline?
Yes, that is in the pipeline: https://lore.kernel.org/lkml/1675774098-17722-1-git-send-email-george.kennedy@oracle.com/
Linus suggested the fix, which was tested and submitted.
Jiri commented on the patch, which I believe was directed at Linus as he suggested the fix.
George > > I also tested the patch proposed by Linus as attachment and that works. > (The small inline patch snippet doesn't) > >>> 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> >>> >>> --- >>> >>> @Storm Could you validate this patch? >>> --- >>> drivers/tty/vt/vc_screen.c | 5 +++-- >>> 1 file changed, 3 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/tty/vt/vc_screen.c b/drivers/tty/vt/vc_screen.c >>> index f566eb1839dc..2ef519a40a87 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) >>> + if (!vc) { >>> + ret = -ENXIO; >>> goto unlock_out; >>> + } >>> /* Check whether we are above size each round, >>> * as copy_to_user at the end of this loop >>> >>> base-commit: c9c3395d5e3dcc6daee66c6908354d47bf98cb0c >> -- >> js >> suse labs >>
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