Messages in this thread | | | Date | Fri, 6 Sep 2013 12:59:47 +0200 | Subject | Re: [PATCH] x86: simplefb: avoid overflow | From | Geert Uytterhoeven <> |
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On Fri, Sep 6, 2013 at 11:55 AM, David Herrmann <dh.herrmann@gmail.com> wrote: > On Fri, Sep 6, 2013 at 11:32 AM, Tom Gundersen <teg@jklm.no> wrote: >> lfb_size can easily be say 4M, which would make the bitshit overflow and >> the test fail. >> >> Signed-off-by: Tom Gundersen <teg@jklm.no> >> Cc: David Herrmann <dh.herrmann@gmail.com> >> Cc: H. Peter Anvin <hpa@zytor.com> >> --- >> arch/x86/kernel/sysfb_simplefb.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/x86/kernel/sysfb_simplefb.c b/arch/x86/kernel/sysfb_simplefb.c >> index 22513e9..fff44a5 100644 >> --- a/arch/x86/kernel/sysfb_simplefb.c >> +++ b/arch/x86/kernel/sysfb_simplefb.c >> @@ -72,7 +72,7 @@ __init int create_simplefb(const struct screen_info *si, >> * the part that is occupied by the framebuffer */ >> len = mode->height * mode->stride; >> len = PAGE_ALIGN(len); >> - if (len > si->lfb_size << 16) { >> + if (len > ((unsigned long) si->lfb_size) << 16) {
On 32-bit, "unsigned long" is the same size as __u32, so this doesn't make any difference.
> Nice catch. vesafb uses "lfb_size * 65535" which causes an implicit > cast. I thought <<16 looks nicer but that doesn't do any implicit > cast..
"lfb_size * 65535" is the same. "lfb_size" is __u32, "65535" is int. So there's no implicit cast. Or am I missing something?
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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