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bpo-32777: subprocess: Fix usage of _Py_set_inheritable() in child_exec() by izbyshev · Pull Request #5560 · python/cpython

…ec()

_Py_set_inheritable() raises a Python-level exception on error and
thus is not async-signal-safe, but child_exec() must use only
async-signal-safe functions because it's executed between fork() and
exec().

Fix this by introducing a non-raising version of _Py_set_inheritable()
and using it throughout child_exec().

@gpshead 

ioctl() is not async-signal-safe, so avoid using that "fast"-path when
we are asked not to raise an exception (currently the only indicator the
API has).
It better describes the actual purpose of the API.

miss-islington pushed a commit to miss-islington/cpython that referenced this pull request

Feb 6, 2018 
…GH-5560)

Fix a rare but potential pre-exec child process deadlock in subprocess on POSIX systems when marking file descriptors inheritable on exec in the child process.  This bug appears to have been introduced in 3.4 with the inheritable file descriptors support.

This also changes Python/fileutils.c `set_inheritable` to use the "slow" two `fcntl` syscall path instead of the "fast" single `ioctl` syscall path when asked to be async signal safe (by way of being asked not to raise exceptions).  `ioctl` is not a POSIX async-signal-safe approved function.

ref: http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html
(cherry picked from commit c1e46e9)

Co-authored-by: Alexey Izbyshev <izbyshev@users.noreply.github.com>

miss-islington pushed a commit to miss-islington/cpython that referenced this pull request

Feb 6, 2018 
…GH-5560)

Fix a rare but potential pre-exec child process deadlock in subprocess on POSIX systems when marking file descriptors inheritable on exec in the child process.  This bug appears to have been introduced in 3.4 with the inheritable file descriptors support.

This also changes Python/fileutils.c `set_inheritable` to use the "slow" two `fcntl` syscall path instead of the "fast" single `ioctl` syscall path when asked to be async signal safe (by way of being asked not to raise exceptions).  `ioctl` is not a POSIX async-signal-safe approved function.

ref: http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html
(cherry picked from commit c1e46e9)

Co-authored-by: Alexey Izbyshev <izbyshev@users.noreply.github.com>

gpshead pushed a commit that referenced this pull request

Feb 6, 2018 
… (GH-5562)

Fix a rare but potential pre-exec child process deadlock in subprocess on POSIX systems when marking file descriptors inheritable on exec in the child process.  This bug appears to have been introduced in 3.4 with the inheritable file descriptors support.

This also changes Python/fileutils.c `set_inheritable` to use the "slow" two `fcntl` syscall path instead of the "fast" single `ioctl` syscall path when asked to be async signal safe (by way of being asked not to raise exceptions).  `ioctl` is not a POSIX async-signal-safe approved function.

ref: http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html
(cherry picked from commit c1e46e9)

Co-authored-by: Alexey Izbyshev <izbyshev@users.noreply.github.com>

gpshead pushed a commit that referenced this pull request

Feb 6, 2018 
… (GH-5563)

Fix a rare but potential pre-exec child process deadlock in subprocess on POSIX systems when marking file descriptors inheritable on exec in the child process.  This bug appears to have been introduced in 3.4 with the inheritable file descriptors support.

This also changes Python/fileutils.c `set_inheritable` to use the "slow" two `fcntl` syscall path instead of the "fast" single `ioctl` syscall path when asked to be async signal safe (by way of being asked not to raise exceptions).  `ioctl` is not a POSIX async-signal-safe approved function.

ref: http://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html
(cherry picked from commit c1e46e9)

Co-authored-by: Alexey Izbyshev <izbyshev@users.noreply.github.com>