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ASAN false positives due to vfork() with GCC 9 #103726
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@colesbury Can I take a look at it?
(Or if you prefer to submit the patch, it will be great)Reacted by Sam Grossbonus points if this can be done only under compiler versions known too old to ASAN the vfork code path so that we retain coverage of what actually gets used when possible.
The CPython GitHub actions ASAN runner currently uses GCC 9.4.0, so it does not properly handle vfork().
But if I understand the issue correctly, what about just upgrading the GCC version by using the apt command for the ASAN tests?
Ah okay, now I understood what the title meant
Disable vfork() when running under ASAN.
It will be great if we can only disable vfork() under ASAN for old gcc versions.Can I take a look at it?
@corona10 - that would be great.
bonus points if this can be done only under compiler versions known too old to ASAN the vfork code path
We might also want to check the Clang version. I believe that Clang 9.0 and newer support vfork() properly:
But if I understand the issue correctly, what about just upgrading the GCC version by using the apt command for the ASAN tests?
That should work, but that means that if someone is running ASAN with an older compiler locally they may run into false positives. (That might be OK -- we could instruct people to use a newer compiler). I'm not sure which approach is better.
Reacted by Donghee Na and Gregory P. SmithReacted by Donghee Nai'm not too worried about people using old toolchains for modern features such as ASAN. Our advice can simply be "upgrade". In my potentially biased experience people who understand what sanitizers are want the recent features and fixes for those to get more accurate results. So if just upgrading our CI and bot configs to use a more recent version is all it takes, sounds good to me.
Reacted by Sam Gross and Donghee NaSo if just upgrading our CI and bot configs to use a more recent version is all it takes, sounds good to me.
+1, I will submit the PR for it
@arhadthedev I think that this is highly related to build rather than extension modules.
- changed the title
[-]Disable vfork() when running under ASAN[/-][+]ASAN false positives due to vfork() with GCC 9[/+]on Apr 24, 2023 I edited the issue title - I hope this is more clear (and doesn't confuse things).
Reacted by Donghee Na and Oleg IaryginNow we can close the issue. Thanks for the report @colesbury
Older versions of ASAN don't properly support
vfork(). Python usesvfork()when available in_posixsubprocess.c. This can lead to false positive reports from ASAN. I believe this issue exists with GCC 9 (and older), but not GCC 10 (and newer). The CPython GitHub actions ASAN runner currently uses GCC 9.4.0, so it does not properly handle vfork().I've seen these false positives in my nogil-3.12 fork. I'm unsure if you've run into them upstream.
See google/sanitizers#925
cpython/Modules/_posixsubprocess.c
Lines 43 to 49 in 5041c2b
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