Revision 59771079c18c44e39106f0f30054025acafadb41 authored by Linus Torvalds on 19 December 2012, 15:18:35 UTC, committed by Linus Torvalds on 19 December 2012, 15:18:35 UTC
Commit 8dd2cb7e880d ("block: discard granularity might not be power of 2") changed a couple of 'binary and' operations into modulus operations. Which turned the harmless case of a zero discard_granularity into a possible divide-by-zero. The code also had a much more subtle bug: it was doing the modulus of a value in bytes using 'sector_t'. That was always conceptually wrong, but didn't actually matter back when the code assumed a power-of-two granularity: we only looked at the low bits anyway. But with potentially arbitrary sector numbers, using a 'sector_t' to express bytes is very very wrong: depending on configuration it limits the starting offset of the device to just 32 bits, and any overflow would result in a wrong value if the modulus wasn't a power-of-two. So re-write the code to not only protect against the divide-by-zero, but to do the starting sector arithmetic in sectors, and using the proper types. [ For any mathematicians out there: it also looks monumentally stupid to do the 'modulo granularity' operation *twice*, never mind having a "+ granularity" in the second modulus op. But that's the easiest way to avoid negative values or overflow, and it is how the original code was done. ] Reported-by: Ingo Molnar <mingo@kernel.org> Reported-by: Doug Anderson <dianders@chromium.org> Cc: Neil Brown <neilb@suse.de> Cc: Shaohua Li <shli@fusionio.com> Acked-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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00-INDEX | -rw-r--r-- | 2.3 KB |
api.txt | -rw-r--r-- | 11.9 KB |
arkfb.txt | -rw-r--r-- | 2.0 KB |
aty128fb.txt | -rw-r--r-- | 2.1 KB |
cirrusfb.txt | -rw-r--r-- | 1.9 KB |
cmap_xfbdev.txt | -rw-r--r-- | 1.9 KB |
deferred_io.txt | -rw-r--r-- | 3.0 KB |
efifb.txt | -rw-r--r-- | 593 bytes |
ep93xx-fb.txt | -rw-r--r-- | 4.2 KB |
fbcon.txt | -rw-r--r-- | 11.5 KB |
framebuffer.txt | -rw-r--r-- | 14.0 KB |
gxfb.txt | -rw-r--r-- | 1.2 KB |
intel810.txt | -rw-r--r-- | 8.3 KB |
intelfb.txt | -rw-r--r-- | 3.7 KB |
internals.txt | -rw-r--r-- | 2.6 KB |
lxfb.txt | -rw-r--r-- | 1.2 KB |
matroxfb.txt | -rw-r--r-- | 19.1 KB |
metronomefb.txt | -rw-r--r-- | 2.0 KB |
modedb.txt | -rw-r--r-- | 6.7 KB |
pvr2fb.txt | -rw-r--r-- | 2.2 KB |
pxafb.txt | -rw-r--r-- | 4.6 KB |
s3fb.txt | -rw-r--r-- | 2.5 KB |
sa1100fb.txt | -rw-r--r-- | 1.3 KB |
sh7760fb.txt | -rw-r--r-- | 4.4 KB |
sisfb.txt | -rw-r--r-- | 6.3 KB |
sm501.txt | -rw-r--r-- | 291 bytes |
sstfb.txt | -rw-r--r-- | 6.7 KB |
tgafb.txt | -rw-r--r-- | 2.4 KB |
tridentfb.txt | -rw-r--r-- | 2.6 KB |
udlfb.txt | -rw-r--r-- | 7.0 KB |
uvesafb.txt | -rw-r--r-- | 6.9 KB |
vesafb.txt | -rw-r--r-- | 6.1 KB |
viafb.modes | -rw-r--r-- | 30.8 KB |
viafb.txt | -rw-r--r-- | 9.6 KB |
vt8623fb.txt | -rw-r--r-- | 1.8 KB |
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