Fix bug processing bmp bit masks

Fix bug processing bmp bit masks

BUG=skia:4866
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1688003002

Committed: https://skia.googlesource.com/skia/+/02b407b744d40f93ecc978bb9f64a5ffb075b82e

[msarett, 2016-02-10 20:49:14]

Description was changed from

==========
Fix bug processing bmp bit masks

BUG=skia:4866
==========

to

==========
Fix bug processing bmp bit masks

BUG=skia:4866
GOLD_TRYBOT_URL=
https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&is...
==========

[msarett, 2016-02-10 20:50:46]

Patchset #1 (id:1) has been deleted

[msarett, 2016-02-10 20:54:26]

Patchset #1 (id:20001) has been deleted

[msarett, 2016-02-10 20:59:27]

msarett@google.com changed reviewers:
+ kjlubick@google.com, scroggo@google.com

[msarett, 2016-02-10 20:59:28]

First win for the fuzzer!

Kevin, please keep the bugs coming!

https://codereview.chromium.org/1688003002/diff/40001/src/codec/SkMasks.cpp
File src/codec/SkMasks.cpp (left):

https://codereview.chromium.org/1688003002/diff/40001/src/codec/SkMasks.cpp#o...
src/codec/SkMasks.cpp:90: // Trim the masks to the allowed number of bits
Unrelated to the bug fix.  We do this is CreateMasks - no reason to repeat it
here.

https://codereview.chromium.org/1688003002/diff/40001/src/codec/SkMasks.cpp
File src/codec/SkMasks.cpp (right):

https://codereview.chromium.org/1688003002/diff/40001/src/codec/SkMasks.cpp#n...
src/codec/SkMasks.cpp:50: static uint8_t convert_to_8(uint8_t component,
uint32_t n) {
No reason for "component" to ever be larger than 8 bits.

This would have prevented the crash.

https://codereview.chromium.org/1688003002/diff/40001/src/codec/SkMasks.cpp#n...
src/codec/SkMasks.cpp:106: // Finish processing the mask
Even if the mask is not continuous, let's count all the bits at the top.

https://codereview.chromium.org/1688003002/diff/40001/src/codec/SkMasks.cpp#n...
src/codec/SkMasks.cpp:115: mask &= 0xFF << shift;
Make sure that the final mask is no larger than 8-bits.

[scroggo, 2016-02-10 21:04:12]

lgtm

[msarett, 2016-02-10 21:09:36]

The CQ bit was checked by msarett@google.com

[commit-bot: I haz the power, 2016-02-10 21:09:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1688003002/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1688003002/40001

[commit-bot: I haz the power, 2016-02-10 21:40:13]

Description was changed from

==========
Fix bug processing bmp bit masks

BUG=skia:4866
GOLD_TRYBOT_URL=
https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&is...
==========

to

==========
Fix bug processing bmp bit masks

BUG=skia:4866
GOLD_TRYBOT_URL=
https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&is...

Committed:
https://skia.googlesource.com/skia/+/02b407b744d40f93ecc978bb9f64a5ffb075b82e
==========

[commit-bot: I haz the power, 2016-02-10 21:40:14]

Committed patchset #1 (id:40001) as
https://skia.googlesource.com/skia/+/02b407b744d40f93ecc978bb9f64a5ffb075b82e