Multiprocessing resource tracker incorrectly checks pipe write length

[grgsrs]

cpython/Lib/multiprocessing/resource_tracker.py

Line 164 in 4781535

if len(name) > 512:

I think this line should be:

if len(msg) > 512:

[saito828koki]

@grgsrs
Thanks for your report!

Your suggestion seems to be correct. To guarantee that a write operation is atomic, the length of msg has to be less than or equal to PIPE_BUF(the kernel pipe buffer size).
According to this page, the minimum acceptable value of PIPE_BUF is set to 512 bytes in POSIX system , so checking if len(msg) is not greater than 512 is enough.

I will create a PR for this issue.

[grgsrs]

Thanks for responding so quickly and glad to help (if only in a very small way).

…

On Sat, 17 Sep 2022 at 7:11 pm, Koki Saito ***@***.***> wrote: @grgsrs <https://github.com/grgsrs> Thanks for your report! Your suggestion seems to be correct. To guarantee that a write operation is atomic, the length of msg has to be less than or equal to PIPE_BUF(the kernel pipe buffer size). According to this page <https://man7.org/linux/man-pages/man7/pipe.7.html>, the minimum acceptable value of PIPE_BUF is set to 512 bytes in POSIX system , so checking if len(msg) is not greater than 512 is enough. I will create a PR for this issue. — Reply to this email directly, view it on GitHub <#96819 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAN26F3OTN34Z2FUYN3NP4DV6WDN5ANCNFSM6AAAAAAQMEMOBM> . You are receiving this because you were mentioned.Message ID: ***@***.***>