x86/boot: Prevent faulty bootparams.screeninfo from causing harm
authorJan H. Schönherr <jschoenh@amazon.de>
Sun, 27 Aug 2017 18:23:43 +0000 (20:23 +0200)
committerIngo Molnar <mingo@kernel.org>
Tue, 29 Aug 2017 11:32:50 +0000 (13:32 +0200)
commitfb1cc2f91664fd8a2e454970480b5413725919f1
treefce72809a3f0b6248af9f98c0f98323163ef0b86
parent5746f0555d00e1cbb7bc20a2fd09041ace6f350c
x86/boot: Prevent faulty bootparams.screeninfo from causing harm

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>
arch/x86/boot/compressed/misc.c