commit 7c90d3d4b39fcf19253e161bd74601f6a8fb6e20
author Daniel Cheng <dcheng@chromium.org> Tue Nov 07 23:17:01 2023
committer Chromium LUCI CQ <chromium-scoped@luci-project-accounts.iam.gserviceaccount.com> Tue Nov 07 23:17:01 2023
tree 62a44acd0b313d86585f502ce7d3f625dbc77dc8
parent 681e585407664232efebceaee369777d22e56b04

Initialize CoderErrorMgr when decoding JPEGs.

Initialize CoderErrorMgr when decoding JPEGs.

gfx::JPEGCodec::Decode() creates an uninitialized `CoderErrorMsg`, which
contains a `jpeg_error_mgr`, which contains a `msg_parm` union. This
union is used much later inside libjpeg_turbo:

   // From third_party/libjpeg_turbo/jerror.c:175:
   SNPRINTF(buffer, JMSG_LENGTH_MAX, msgtext,
            err->msg_parm.i[0], err->msg_parm.i[1],
            err->msg_parm.i[2], err->msg_parm.i[3],
            err->msg_parm.i[4], err->msg_parm.i[5],
            err->msg_parm.i[6], err->msg_parm.i[7]);

libjpeg_turbo only initializes as many `msg_parm.i` entries as the
corresponding format specifier consumes, relying on `SNPRINTF()` to
ignore extra arguments. However, MSan still warns that this is a use of
an uninitialized value, and indeed, the C standard says:

   If the format is exhausted while arguments remain, the excess
   arguments are evaluated (as always) but are otherwise ignored.

Bug: 1369167
Change-Id: I35ac2bf7eecea6152d765de2015261f33cbe6615
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5008686
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1221255}