[pull] master from php:master - #1225
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Freeing the same small pointer twice in a row pushed it onto the freelist twice, so the next two allocations of that bin returned the same address. That's a nifty primitive to obtain two live pointers of different types to the same object. The shadow-pointer check does not catch it, as both links are consistent. This commit adds a simple check for when the freed pointer already is the head of the freelist. heap->free_slot[bin_num] is loaded by the very next line, so the check costs a single comparison on an already-hot value. This only catches consecutive double-frees, not a free after other activity on the same bin, but it doesn't cost ~anything performance wise, and catches real bugs like error/cleanup paths freeing the same value twice. A quick look at `git log --grep='double.free'` shows that this is a popular bug pattern.
PHPDBG_G(watch_recreation) is keyed by element->str, so a watch element and
its implicit parent are stored under distinct keys ("$lower[0]" and
"$lower[]"). The deduplication in phpdbg_queue_element_for_recreation() only
walks down from the entry found under the *same* key, so it never notices
that the two belong to the same chain and both get queued.
phpdbg_free_watch_element_tree() frees the element together with its entire
parent and child chains, so draining watch_recreation freed that chain twice:
the first entry frees the whole chain, the second one then walks the already
freed links and frees them again.
Drop every entry referencing a member of the chain before freeing it. The
buckets are nulled out rather than deleted, as all callers are iterating over
the hash at that point; they clean it right afterwards.
See kocsismate/php-version-benchmarks@351e967b1 for details. "bolt_align" (llvm/llvm-project#210634) is an experimental option, but it should basically eliminate any false positive differences due to binary layout changes. The "bolt" option stands for regular BOLT compilation.
An empty Location header allocates a single byte for the NUL terminator, so reading location[1] in the relative-redirect branch over-reads heap memory and could append a garbage-derived path to the redirect target instead of the correct host root. Use location_len instead of strlen, and skip the relative join when location_len is 0, so the second byte is never read. Closes GH-23467
* PHP-8.4: [http] Fix out-of-bounds read on empty Location header
* PHP-8.5: [http] Fix out-of-bounds read on empty Location header
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