Fix GH-22480: phpdbg use-after-free re-watching a watched variable#136
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Fix GH-22480: phpdbg use-after-free re-watching a watched variable#136iliaal wants to merge 1 commit into
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phpdbg_add_watch_element() frees the passed element and returns the existing one when the variable is already watched, but several callers kept using the freed pointer, so re-watching a variable was a use-after-free in more places than the two reported. Report the duplicate back through the parse callback and register nothing, and reject a recursive watch's hashtable element that collides with an existing watch, at creation and recreation, rather than freeing a still-referenced one. A recursive watch over an already-array-watched variable now watches only the root and skips the shared hashtable. Fixes phpGH-22480
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Fixes php#22480
phpdbg_add_watch_element()frees the passed element and returns the existing one when the variable is already watched, but several callers kept using the freed pointer, so re-watching a variable was a use-after-free. The two reported derefs are not the whole bug: with only the proposed two-line capture,w a $atyped twice still crashes, relocated to a later interned-string read. This reports the duplicate back through the parse callback so the wrapper registers nothing, and rejects a recursive watch's hashtable element that collides with an existing watch, at creation and recreation, instead of freeing a still-referenced one.