Bug 428364

Summary: Signals inside io_uring_enter not handled
Product: [Developer tools] valgrind Reporter: Andrew Soutar <kdebugtraq>
Component: generalAssignee: Julian Seward <jseward>
Status: RESOLVED FIXED    
Severity: crash CC: lomakin.andrey, pjfloyd
Priority: NOR    
Version First Reported In: unspecified   
Target Milestone: ---   
Platform: unspecified   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: [PATCH] Handle signals in epoll_pwait and io_uring_enter

Description Andrew Soutar 2020-10-27 22:02:13 UTC 
Created attachment 132811 [details]
[PATCH] Handle signals in epoll_pwait and io_uring_enter

SUMMARY
I found a couple problems related to signals and the io_uring_enter syscall. First, inside a blocked io_uring_enter#, the traced process will not receive any signals (they remain blocked by Valgrind's internal signal-handling logic). Second, it's possible to crash Valgrind by unblocking signals using the "sig" parameter to io_uring_enter and then sending those signals, as demonstrated below.

STEPS TO REPRODUCE
cat > valgrind_repro_1.c <<'EOF'
#include <stdlib.h>
#include <unistd.h>
#include <err.h>
#include <signal.h>
#include <sys/syscall.h>
#include <linux/io_uring.h>

int main() {
  struct io_uring_params p = { 0 };
  int fd = syscall(SYS_io_uring_setup, 1, &p);
  if (fd < 0)
    err(EXIT_FAILURE, "io_uring_setup");
  syscall(SYS_io_uring_enter, fd, 0, 1, IORING_ENTER_GETEVENTS, NULL, _NSIG / 8);
  for (;;);
}
EOF
cat > valgrind_repro_2.c <<'EOF'
#include <stdlib.h>
#include <unistd.h>
#include <err.h>
#include <signal.h>
#include <sys/syscall.h>
#include <linux/io_uring.h>

int main() {
  sigset_t oldmask;
  struct io_uring_params p = { 0 };
  int fd = syscall(SYS_io_uring_setup, 1, &p);
  if (fd < 0)
    err(EXIT_FAILURE, "io_uring_setup");
  if (sigprocmask(SIG_BLOCK, NULL, &oldmask))
    err(EXIT_FAILURE, "sigprocmask");
  syscall(SYS_io_uring_enter, fd, 0, 1, IORING_ENTER_GETEVENTS, &oldmask, _NSIG / 8);
  for (;;);
}
EOF
gcc -o valgrind-repro-1 valgrind-repro-1.c
gcc -o valgrind-repro-2 valgrind-repro-2.c

OBSERVED RESULT
> uname -a
Linux linux 5.7.11-100.fc31.x86_64 #1 SMP Wed Jul 29 18:17:53 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
> valgrind --version
valgrind-3.16.0

> valgrind ./valgrind_repro_1
==64542== Memcheck, a memory error detector
==64542== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==64542== Using Valgrind-3.16.0-bf5e647edb-20200519X and LibVEX; rerun with -h for copyright info
==64542== Command: ./valgrind_repro_1
==64542== 
--64542-- Valgrind options:
--64542--    -v
--64542-- Contents of /proc/version:
--64542--   Linux version 5.7.11-100.fc31.x86_64 (mockbuild@bkernel01.iad2.fedoraproject.org) (gcc version 9.3.1 20200408 (Red Hat 9.3.1-2) (GCC), GNU ld version 2.32-31.fc31) #1 SMP Wed Jul 29 18:17:53 UTC 2020
--64542-- 
--64542-- Arch and hwcaps: AMD64, LittleEndian, amd64-cx16-lzcnt-rdtscp-sse3-ssse3-avx-avx2-bmi-f16c-rdrand
--64542-- Page sizes: currently 4096, max supported 4096
--64542-- Valgrind library directory: /usr/libexec/valgrind
--64542-- Reading syms from /home/andrewsoutar/src/misc/valgrind_repro_1
--64542-- Reading syms from /usr/lib64/ld-2.30.so
--64542-- Reading syms from /usr/libexec/valgrind/memcheck-amd64-linux
--64542--    object doesn't have a symbol table
--64542--    object doesn't have a dynamic symbol table
--64542-- Scheduler: using generic scheduler lock implementation.
--64542-- Reading suppressions file: /usr/libexec/valgrind/default.supp
==64542== embedded gdbserver: reading from /tmp/vgdb-pipe-from-vgdb-to-64542-by-andrewsoutar-on-linux
==64542== embedded gdbserver: writing to   /tmp/vgdb-pipe-to-vgdb-from-64542-by-andrewsoutar-on-linux
==64542== embedded gdbserver: shared mem   /tmp/vgdb-pipe-shared-mem-vgdb-64542-by-andrewsoutar-on-linux
==64542== 
==64542== TO CONTROL THIS PROCESS USING vgdb (which you probably
==64542== don't want to do, unless you know exactly what you're doing,
==64542== or are doing some strange experiment):
==64542==   /usr/libexec/valgrind/../../bin/vgdb --pid=64542 ...command...
==64542== 
==64542== TO DEBUG THIS PROCESS USING GDB: start GDB like this
==64542==   /path/to/gdb ./valgrind_repro_1
==64542== and then give GDB the following command
==64542==   target remote | /usr/libexec/valgrind/../../bin/vgdb --pid=64542
==64542== --pid is optional if only one valgrind process is running
==64542== 
--64542-- REDIR: 0x4021350 (ld-linux-x86-64.so.2:strlen) redirected to 0x580ccdd2 (???)
--64542-- REDIR: 0x4021120 (ld-linux-x86-64.so.2:index) redirected to 0x580ccdec (???)
--64542-- Reading syms from /usr/libexec/valgrind/vgpreload_core-amd64-linux.so
--64542-- Reading syms from /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so
==64542== WARNING: new redirection conflicts with existing -- ignoring it
--64542--     old: 0x04021350 (strlen              ) R-> (0000.0) 0x580ccdd2 ???
--64542--     new: 0x04021350 (strlen              ) R-> (2007.0) 0x0483cd00 strlen
--64542-- REDIR: 0x401db30 (ld-linux-x86-64.so.2:strcmp) redirected to 0x483dc70 (strcmp)
--64542-- REDIR: 0x40218b0 (ld-linux-x86-64.so.2:mempcpy) redirected to 0x4841790 (mempcpy)
--64542-- Reading syms from /usr/lib64/libc-2.30.so
--64542-- REDIR: 0x4902000 (libc.so.6:memmove) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4901380 (libc.so.6:strncpy) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4902330 (libc.so.6:strcasecmp) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4900ca0 (libc.so.6:strcat) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x49013e0 (libc.so.6:rindex) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x49036d0 (libc.so.6:rawmemchr) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x491bbf0 (libc.so.6:wmemchr) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x491b730 (libc.so.6:wcscmp) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4902160 (libc.so.6:mempcpy) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4901f90 (libc.so.6:bcmp) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4901310 (libc.so.6:strncmp) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4900d50 (libc.so.6:strcmp) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x49020c0 (libc.so.6:memset) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x491b6f0 (libc.so.6:wcschr) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4901270 (libc.so.6:strnlen) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4900e30 (libc.so.6:strcspn) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4902380 (libc.so.6:strncasecmp) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4900dd0 (libc.so.6:strcpy) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x49024d0 (libc.so.6:memcpy@@GLIBC_2.14) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x491ce40 (libc.so.6:wcsnlen) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x491b770 (libc.so.6:wcscpy) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4901420 (libc.so.6:strpbrk) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4900d00 (libc.so.6:index) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4901230 (libc.so.6:strlen) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4907b50 (libc.so.6:memrchr) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x49023d0 (libc.so.6:strcasecmp_l) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4901f50 (libc.so.6:memchr) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x491b840 (libc.so.6:wcslen) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x49016e0 (libc.so.6:strspn) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x49022d0 (libc.so.6:stpncpy) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4902270 (libc.so.6:stpcpy) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4903710 (libc.so.6:strchrnul) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x4902420 (libc.so.6:strncasecmp_l) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64542-- REDIR: 0x49d2740 (libc.so.6:__strrchr_avx2) redirected to 0x483c6b0 (rindex)
^C^C^C [process does not terminate]
> valgrind -v ./valgrind_repro_2
==64546== Memcheck, a memory error detector
==64546== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==64546== Using Valgrind-3.16.0-bf5e647edb-20200519X and LibVEX; rerun with -h for copyright info
==64546== Command: ./valgrind_repro_2
==64546== 
--64546-- Valgrind options:
--64546--    -v
--64546-- Contents of /proc/version:
--64546--   Linux version 5.7.11-100.fc31.x86_64 (mockbuild@bkernel01.iad2.fedoraproject.org) (gcc version 9.3.1 20200408 (Red Hat 9.3.1-2) (GCC), GNU ld version 2.32-31.fc31) #1 SMP Wed Jul 29 18:17:53 UTC 2020
--64546-- 
--64546-- Arch and hwcaps: AMD64, LittleEndian, amd64-cx16-lzcnt-rdtscp-sse3-ssse3-avx-avx2-bmi-f16c-rdrand
--64546-- Page sizes: currently 4096, max supported 4096
--64546-- Valgrind library directory: /usr/libexec/valgrind
--64546-- Reading syms from /home/andrewsoutar/src/misc/valgrind_repro_2
--64546-- Reading syms from /usr/lib64/ld-2.30.so
--64546-- Reading syms from /usr/libexec/valgrind/memcheck-amd64-linux
--64546--    object doesn't have a symbol table
--64546--    object doesn't have a dynamic symbol table
--64546-- Scheduler: using generic scheduler lock implementation.
--64546-- Reading suppressions file: /usr/libexec/valgrind/default.supp
==64546== embedded gdbserver: reading from /tmp/vgdb-pipe-from-vgdb-to-64546-by-andrewsoutar-on-linux
==64546== embedded gdbserver: writing to   /tmp/vgdb-pipe-to-vgdb-from-64546-by-andrewsoutar-on-linux
==64546== embedded gdbserver: shared mem   /tmp/vgdb-pipe-shared-mem-vgdb-64546-by-andrewsoutar-on-linux
==64546== 
==64546== TO CONTROL THIS PROCESS USING vgdb (which you probably
==64546== don't want to do, unless you know exactly what you're doing,
==64546== or are doing some strange experiment):
==64546==   /usr/libexec/valgrind/../../bin/vgdb --pid=64546 ...command...
==64546== 
==64546== TO DEBUG THIS PROCESS USING GDB: start GDB like this
==64546==   /path/to/gdb ./valgrind_repro_2
==64546== and then give GDB the following command
==64546==   target remote | /usr/libexec/valgrind/../../bin/vgdb --pid=64546
==64546== --pid is optional if only one valgrind process is running
==64546== 
--64546-- REDIR: 0x4021350 (ld-linux-x86-64.so.2:strlen) redirected to 0x580ccdd2 (???)
--64546-- REDIR: 0x4021120 (ld-linux-x86-64.so.2:index) redirected to 0x580ccdec (???)
--64546-- Reading syms from /usr/libexec/valgrind/vgpreload_core-amd64-linux.so
--64546-- Reading syms from /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so
==64546== WARNING: new redirection conflicts with existing -- ignoring it
--64546--     old: 0x04021350 (strlen              ) R-> (0000.0) 0x580ccdd2 ???
--64546--     new: 0x04021350 (strlen              ) R-> (2007.0) 0x0483cd00 strlen
--64546-- REDIR: 0x401db30 (ld-linux-x86-64.so.2:strcmp) redirected to 0x483dc70 (strcmp)
--64546-- REDIR: 0x40218b0 (ld-linux-x86-64.so.2:mempcpy) redirected to 0x4841790 (mempcpy)
--64546-- Reading syms from /usr/lib64/libc-2.30.so
--64546-- REDIR: 0x4902000 (libc.so.6:memmove) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4901380 (libc.so.6:strncpy) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4902330 (libc.so.6:strcasecmp) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4900ca0 (libc.so.6:strcat) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x49013e0 (libc.so.6:rindex) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x49036d0 (libc.so.6:rawmemchr) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x491bbf0 (libc.so.6:wmemchr) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x491b730 (libc.so.6:wcscmp) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4902160 (libc.so.6:mempcpy) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4901f90 (libc.so.6:bcmp) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4901310 (libc.so.6:strncmp) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4900d50 (libc.so.6:strcmp) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x49020c0 (libc.so.6:memset) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x491b6f0 (libc.so.6:wcschr) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4901270 (libc.so.6:strnlen) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4900e30 (libc.so.6:strcspn) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4902380 (libc.so.6:strncasecmp) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4900dd0 (libc.so.6:strcpy) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x49024d0 (libc.so.6:memcpy@@GLIBC_2.14) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x491ce40 (libc.so.6:wcsnlen) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x491b770 (libc.so.6:wcscpy) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4901420 (libc.so.6:strpbrk) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4900d00 (libc.so.6:index) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4901230 (libc.so.6:strlen) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4907b50 (libc.so.6:memrchr) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x49023d0 (libc.so.6:strcasecmp_l) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4901f50 (libc.so.6:memchr) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x491b840 (libc.so.6:wcslen) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x49016e0 (libc.so.6:strspn) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x49022d0 (libc.so.6:stpncpy) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4902270 (libc.so.6:stpcpy) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4903710 (libc.so.6:strchrnul) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x4902420 (libc.so.6:strncasecmp_l) redirected to 0x482f1e1 (_vgnU_ifunc_wrapper)
--64546-- REDIR: 0x49d2740 (libc.so.6:__strrchr_avx2) redirected to 0x483c6b0 (rindex)

^C
valgrind: m_signals.c:2446 (async_signalhandler): Assertion 'tst->status == VgTs_WaitSys' failed.

host stacktrace:
==64546==    at 0x580480CA: ??? (in /usr/libexec/valgrind/memcheck-amd64-linux)
==64546==    by 0x580481F7: ??? (in /usr/libexec/valgrind/memcheck-amd64-linux)
==64546==    by 0x5804839B: ??? (in /usr/libexec/valgrind/memcheck-amd64-linux)
==64546==    by 0x5805B674: ??? (in /usr/libexec/valgrind/memcheck-amd64-linux)
==64546==    by 0x5805962F: ??? (in /usr/libexec/valgrind/memcheck-amd64-linux)
==64546==    by 0x6: ???

sched status:
  running_tid=1

Thread 1: status = VgTs_Runnable syscall 426 (lwpid 64546)
==64546==    at 0x496D1DD: syscall (in /usr/lib64/libc-2.30.so)
==64546==    by 0x401207: main (in /home/andrewsoutar/src/misc/valgrind_repro_2)
client stack range: [0x1FFEFFD000 0x1FFF000FFF] client SP: 0x1FFEFFF418
valgrind stack range: [0x1002AA6000 0x1002BA5FFF] top usage: 7464 of 1048576


Note: see also the FAQ in the source distribution.
It contains workarounds to several common problems.
In particular, if Valgrind aborted or crashed after
identifying problems in your program, there's a good chance
that fixing those problems will prevent Valgrind aborting or
crashing, especially if it happened in m_mallocfree.c.

If that doesn't help, please report this bug to: www.valgrind.org

In the bug report, send all the above text, the valgrind
version, and what OS and version you are using.  Thanks.


EXPECTED RESULT
> valgrind ./valgrind_repro_1
==64252== Memcheck, a memory error detector
==64252== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==64252== Using Valgrind-3.17.0.GIT and LibVEX; rerun with -h for copyright info
==64252== Command: ./valgrind_repro_1
==64252== 
^C==64252== 
==64252== Process terminating with default action of signal 2 (SIGINT)
==64252==    at 0x496C1DD: syscall (in /usr/lib64/libc-2.30.so)
==64252==    by 0x4011B9: main (in /home/andrewsoutar/src/misc/valgrind_repro_1)
==64252== 
==64252== HEAP SUMMARY:
==64252==     in use at exit: 0 bytes in 0 blocks
==64252==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==64252== 
==64252== All heap blocks were freed -- no leaks are possible
==64252== 
==64252== For lists of detected and suppressed errors, rerun with: -s
==64252== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

> valgrind ./valgrind_repro_2
==64291== Memcheck, a memory error detector
==64291== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==64291== Using Valgrind-3.17.0.GIT and LibVEX; rerun with -h for copyright info
==64291== Command: ./valgrind_repro_2
==64291== 
^C==64291== 
==64291== Process terminating with default action of signal 2 (SIGINT)
==64291==    at 0x496C1DD: syscall (in /usr/lib64/libc-2.30.so)
==64291==    by 0x401207: main (in /home/andrewsoutar/src/misc/valgrind_repro_2)
==64291== 
==64291== HEAP SUMMARY:
==64291==     in use at exit: 0 bytes in 0 blocks
==64291==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==64291== 
==64291== All heap blocks were freed -- no leaks are possible
==64291== 
==64291== For lists of detected and suppressed errors, rerun with: -s
==64291== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

SOFTWARE/OS VERSIONS
Fedora 31
Linux linux 5.7.11-100.fc31.x86_64 #1 SMP Wed Jul 29 18:17:53 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
valgrind-3.16.0 (for some reason 3.15-SVN is the latest version available in the version field)

ADDITIONAL INFORMATION
I've attached a patch against master that fixes the issue for me, as well as making sure SIGVGKILL etc. don't get blocked by io_uring_enter and epoll_pwait. It basically just uses logic factored out of the ppoll syswrap, so there may be a better way to do this.
Comment 1 Paul Floyd 2023-11-18 12:07:26 UTC 
commit c49efc1cff161a8cfa741900c262f5b1c03f82b3 (HEAD -> master, origin/master, origin/HEAD)
Author: Paul Floyd <pjfloyd@wanadoo.fr>
Date:   Sat Nov 18 13:02:30 2023 +0100

    Bug 428364 - Signals inside io_uring_enter not handled
    
    Patch provide by
        Andrew Soutar kdebugtraq@andrewsoutar.com
    Thanks!
    
    I haven't added the reproducers as they require interrupting
    the Valgrind process. Maybe the tests can be adapted to use
    fork and have the parent kill the child running io_uring.