ext/gd: fix out-of-bounds write reading font header on short reads#101
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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#101iliaal 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.
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Submitted upstream as php#22380. |
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imageloadfont() indexed the header read destination as
(char*)&font[b], which scales the byte counter by sizeof(gdFont) instead of advancing one byte, so a short php_stream_read (a user stream wrapper is enough) writes hdr_size-b bytes past the emalloc(sizeof(gdFont)) buffer. The added test drips a valid 1x1 font one byte per read: on stock the load fails and USE_ZEND_ALLOC=0 valgrind reports an invalid write at gd.c:559, with the fix it loads and valgrind is clean.