Fix EXIF bugs where corrupted exif blocks could overrun memory #3627
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In one case, we actually had a check for this, but an assignment to an int made the nonsensical offset appear negative, and we only tested whether the necessary offset it was bigger than the buffer size. Keeping it as (unsigned) size_t makes the test work as intended. In another case, there were several places where we never checked that we were staying within the exif block, and here we address this by changing the utility decode_ifd so instead of passing it a pointer to the ifd, it passes the offset (the pointer turned out to always be inside the buffer) so it can check the extent for subsequent accesses. Also some fixes related to squashing undefined behavior sanitizer cases.
lgritz
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Oct 22, 2022
…mySoftwareFoundation#3627) In one case, we actually had a check for this, but an assignment to an int made the nonsensical offset appear negative, and we only tested whether the necessary offset it was bigger than the buffer size. Keeping it as (unsigned) size_t makes the test work as intended. In another case, there were several places where we never checked that we were staying within the exif block, and here we address this by changing the utility decode_ifd so instead of passing it a pointer to the ifd, it passes the offset (the pointer turned out to always be inside the buffer) so it can check the extent for subsequent accesses. Also some fixes related to squashing undefined behavior sanitizer cases.
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In one case, we actually had a check for this, but an assignment to an int made the nonsensical offset appear negative, and we only tested whether the necessary offset it was bigger than the buffer size. Keeping it as (unsigned) size_t makes the test work as intended.
In another case, there were several places where we never checked that we were staying within the exif block, and here we address this by changing the utility decode_ifd so instead of passing it a pointer to the ifd, it passes the offset (the pointer turned out to always be inside the buffer) so it can check the extent for subsequent accesses.
Also some fixes related to squashing undefined behavior sanitizer cases.