[Bug 1896281] Re: glibc 2.32 leaks errno in sched_rr_get_interval fallback

[Balint Reczey]

** Changed in: glibc (Ubuntu)
   Importance: Medium => Low

** Changed in: glibc (Ubuntu Groovy)
   Importance: Medium => Low

** Changed in: glibc (Ubuntu)
       Status: New => Invalid

** Changed in: glibc (Ubuntu Groovy)
       Status: New => Invalid

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Title:
  glibc 2.32 leaks errno in sched_rr_get_interval fallback

Status in GLibC:
  Invalid
Status in glibc package in Ubuntu:
  Invalid
Status in unhide package in Ubuntu:
  Fix Released
Status in glibc source package in Groovy:
  Invalid
Status in unhide source package in Groovy:
  Fix Released

Bug description:
  root at autopkgtest-lxd-rygyvj:/tmp/autopkgtest.Pui0CD/build.uqw/src# strace ./a.out 
  execve("./a.out", ["./a.out"], 0xfff2c8a0 /* 12 vars */) = 0
  brk(NULL)                               = 0x1942000
  uname({sysname="Linux", nodename="autopkgtest-lxd-rygyvj", ...}) = 0
  access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
  openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3
  fstat64(3, {st_mode=S_IFREG|0644, st_size=24113, ...}) = 0
  mmap2(NULL, 24113, PROT_READ, MAP_PRIVATE, 3, 0) = 0xf78ec000
  close(3)                                = 0
  openat(AT_FDCWD, "/lib/arm-linux-gnueabihf/libc.so.6", O_RDONLY|O_LARGEFILE|O_CLOEXEC) = 3
  read(3, "\177ELF\1\1\1\3\0\0\0\0\0\0\0\0\3\0(\0\1\0\0\0\t\261\1\0004\0\0\0"..., 512) = 512
  fstat64(3, {st_mode=S_IFREG|0755, st_size=988544, ...}) = 0
  mmap2(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xf78ea000
  mmap2(NULL, 1054788, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xf77c6000
  mprotect(0xf78b3000, 61440, PROT_NONE)  = 0
  mmap2(0xf78c2000, 16384, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0xec000) = 0xf78c2000
  mmap2(0xf78c6000, 6212, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xf78c6000
  close(3)                                = 0
  set_tls(0xf78eac90)                     = 0
  mprotect(0xf78c2000, 8192, PROT_READ)   = 0
  mprotect(0x81b000, 4096, PROT_READ)     = 0
  mprotect(0xf78f2000, 4096, PROT_READ)   = 0
  munmap(0xf78ec000, 24113)               = 0
  sched_rr_get_interval_time64(1, 0xfff88678) = -1 ENOSYS (Function not implemented)
  sched_rr_get_interval(1, {tv_sec=0, tv_nsec=0}) = 0
  dup(2)                                  = 3
  fcntl64(3, F_GETFL)                     = 0x402 (flags O_RDWR|O_APPEND)
  brk(NULL)                               = 0x1942000
  brk(0x1963000)                          = 0x1963000
  fstat64(3, {st_mode=S_IFCHR|0620, st_rdev=makedev(0x88, 0x3), ...}) = 0
  write(3, "error: Function not implemented\n", 32error: Function not implemented
  ) = 32
  close(3)                                = 0
  exit_group(0)                           = ?
  +++ exited with 0 +++
  root at autopkgtest-lxd-rygyvj:/tmp/autopkgtest.Pui0CD/build.uqw/src# cat test.c 
  #include <stdio.h>
  #include <errno.h>
  #include <sched.h>
  int main() {
    struct timespec tp;
    errno = 0;
    sched_rr_get_interval(1, &tp);
    perror("error");
    return 0;
  }

  When sched_rr_get_interval_time64 is not implemented glibc falls back
  to sched_rr_get_interval syscall but does not clear errno.

  This breaks 'unhide quick' and a few other unhide commands giving
  false positives as a result.

  The problem is observed only on armhf testbeds.

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