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videodsp: fix 1-byte overread in top/bottom READ_NUM_BYTES iterations.

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This can overread (either before start or beyond end) of the buffer in
Nx1 (i.e. height=1) images.

Fixes mozilla bug 1240080.
This commit is contained in:
Ronald S. Bultje 2016-01-16 14:44:28 -05:00
parent 5da1477fa0
commit 0f88b3f82f
1 changed files with 6 additions and 15 deletions
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21
libavcodec/x86/videodsp.asm
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@ -193,14 +193,10 @@ hvar_fn
mov valb, [srcq+%2-1]
%elif (%2-%%off) == 2
mov valw, [srcq+%2-2]
%elifidn %1, body
%else
mov valb, [srcq+%2-1]
sal vald, 16
ror vald, 16
mov valw, [srcq+%2-3]
%elifidn %1, bottom
movd mm %+ %%mmx_idx, [srcq+%2-4]
%else ; top
movd mm %+ %%mmx_idx, [srcq+%2-3]
%endif
%endif ; (%2-%%off) >= 1
%endmacro ; READ_NUM_BYTES
@ -253,18 +249,13 @@ hvar_fn
mov [dstq+%2-1], valb
%elif (%2-%%off) == 2
mov [dstq+%2-2], valw
%elifidn %1, body
mov [dstq+%2-3], valw
sar vald, 16
mov [dstq+%2-1], valb
%else
movd vald, mm %+ %%mmx_idx
%ifidn %1, bottom
sar vald, 8
%endif
mov [dstq+%2-3], valw
sar vald, 16
ror vald, 16
mov [dstq+%2-1], valb
%ifnidn %1, body
ror vald, 16
%endif
%endif
%endif ; (%2-%%off) >= 1
%endmacro ; WRITE_NUM_BYTES