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x86/boot: Prevent faulty bootparams.screeninfo from causing harm

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If a zero for the number of lines manages to slip through, scroll()
may underflow some offset calculations, causing accesses outside the
video memory.

Make the check in __putstr() more pessimistic to prevent that.

Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1503858223-14983-1-git-send-email-jschoenh@amazon.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Jan H. Schönherr 2017-08-27 20:23:43 +02:00 committed by Ingo Molnar
parent 5746f0555d
commit fb1cc2f916
1 changed files with 1 additions and 2 deletions
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3
arch/x86/boot/compressed/misc.c
View file

@ -116,8 +116,7 @@ void __putstr(const char *s)
}
}
if (boot_params->screen_info.orig_video_mode == 0 &&
lines == 0 && cols == 0)
if (lines == 0 || cols == 0)
return;
x = boot_params->screen_info.orig_x;