fix(profiling): fix invalid access in GenInfo::create_impl#17038
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Co-authored-by: KowalskiThomas <14239160+KowalskiThomas@users.noreply.github.com>
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taegyunkim
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Description
https://datadoghq.atlassian.net/browse/PROF-13112
This fixes a segmentation fault / invalid memory read I discovered through Crash Logs.
The problem is similar to others we've already seen in the past;
f->f_lastiwas used to index into a bytecode buffer, butfwas a "real" pointer and not acopy_memory'd one.Since we don't hold the GIL is not held during sampling, this is possibly an invalid read, which seems to happen rarely (I had never seen this before) but can happen.
This should only have happened on Python < 3.11 given what code it is, but it's still worth fixing.
Additionally, neither the Python < 3.10 nor the Python 3.10 code paths performed bounds checking on the computed bytecode index before accessing the
c[]buffer. With stale frame data,frame.f_lastican be an arbitrary value, leading to an out-of-bounds read on the locally-allocated bytecode buffer.Risks
This should remove risks more than it adds. As far as I can tell, it is safe as the only changes are for reading local memory as opposed to unsafe memory.