Fix GH-15980: Signed integer overflow in main/streams/streams.c #15989
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We need to avoid signed integer overflows which are undefined behavior. We catch that, and set `offset` to `ZEND_LONG_MAX` (which is also the largest value of `zend_off_t` on all platforms). Of course, after such a seek a stream is no longer readable, but that matches the current behavior for offsets near `ZEND_LONG_MAX`.
Girgias
reviewed
Sep 22, 2024
Comment on lines
+1358
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| if (UNEXPECTED(offset > ZEND_LONG_MAX - stream->position)) { | ||
| offset = ZEND_LONG_MAX; | ||
| } else { |
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Long term we probably should warn about those large offsets
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Yeah, although it's somewhat hard to determine what is too large. Something like ZEND_LONG_MAX - chunk size may work. (I'm mostly thinking about 32bit systems.)
bukka
approved these changes
Sep 22, 2024
|
The new test case fails on 64bit Linux, so this needs closer investigation; for now I have reverted the commits. |
Closed
For some OS/FS, `fseek()` may fail, so `ftell()` will obviously report the old position.
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We need to avoid signed integer overflows which are undefined behavior. We catch that, and set
offsettoZEND_LONG_MAX(which is also the largest value ofzend_off_ton all platforms). Of course, after such a seek a stream is no longer readable, but that matches the current behavior for offsets nearZEND_LONG_MAX.