ext/gd: fix out-of-bounds write reading font header on short reads#22380
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iliaal wants to merge 1 commit into
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ext/gd: fix out-of-bounds write reading font header on short reads#22380iliaal wants to merge 1 commit into
iliaal wants to merge 1 commit into
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imageloadfont() read the font header with `(char*)&font[b]`, which scales the byte counter b by sizeof(gdFont) rather than advancing one byte, so a short php_stream_read() (deliverable by a user stream wrapper) makes the loop write hdr_size-b bytes past the emalloc(sizeof(gdFont)) buffer. Index the destination by bytes, matching the body read a few lines below.
devnexen
approved these changes
Jun 21, 2026
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The new test fails in nightly on PPC64. Can you please have a look? https://github.com/php/php-src/actions/runs/27996485653/job/82859805119 |
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Test bug, not a code bug. The header was packed with |
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imageloadfont() indexes the header copy with
(char*)&font[b], which scales the byte counter b by sizeof(gdFont) rather than advancing one byte, so a short php_stream_read() (deliverable by a user stream wrapper) writes hdr_size-b bytes past the emalloc(sizeof(gdFont)) buffer. Byte-index the destination to match the body read a few lines below. #15231 rewrites the same loop to read into a sized buffer and would also resolve this, but it has been idle since March, so this is the minimal targeted fix.