[Bug 1770480] Re: preadv2 test does not consider new flag from linux 4.16

[Launchpad Bug Tracker]

This bug was fixed in the package glibc - 2.27-3ubuntu1.3

---------------
glibc (2.27-3ubuntu1.3) bionic; urgency=medium

  [ Balint Reczey ]
  * debian/gbp.conf: Add initial configuration
  * debian/control.in/main: Add Vcs-* pointing to Ubuntu packaging repository
  * arm64: Enable searching shared libraries in atomics/ on LSE HW
  * Ship arm64 variant with LSE support in libc6-lse (LP: #1885012)
  * Run tests of libc6-lse on HW supporting LSE
  * debian/patches/git-updates.diff: update from upstream stable branch
    - pthread_cond_broadcast: Fix waiters-after-spinning case
    - Fix SSe2-based memmove corrupting memory (CVE-2017-18269)
    - Fix strstr() performance regression on Haswell processors
    - Support Japanese new era "令和 (Reiwa)"
    - io: Remove copy_file_range emulation
    (LP: #1851263, #1858203, #1838327, #1797335, #1756209, #1853193)
  * XFAIL stdlib/tst-getrandom (LP: #1891403)
  * debian/testsuite-xfail-debian.mk: XFAIL new tst-support_descriptors

  [ Thadeu Lima de Souza Cascardo ]
  * tests: Make preadwritev2 invalid flags tests unsupported (LP: #1770480)

  [ Andreas Hasenack ]
  * branch-pthread_rwlock_trywrlock-hang-23844.patch:
    nptl: Fix pthread_rwlock_try*lock stalls (Bug 23844) (LP: #1864864)

 -- Balint Reczey <rbalint at ubuntu.com>  Wed, 02 Sep 2020 11:18:37 +0200

** Changed in: glibc (Ubuntu Bionic)
       Status: Fix Committed => Fix Released

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2017-18269

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https://bugs.launchpad.net/bugs/1770480

Title:
  preadv2 test does not consider new flag from linux 4.16

Status in glibc package in Ubuntu:
  Fix Released
Status in glibc source package in Bionic:
  Fix Released
Status in glibc source package in Cosmic:
  Fix Released

Bug description:
  [Impact]
  When tested against newer versions of linux, glibc tests will fail as it makes some assumptions about supportead features on the kernel.

  [Fix]
  Ignore "invalid" (rather unknown) flags success as failure, instead exiting as unsupported (equivalent to skip).

  [Test case]
  Build glibc and run its tests on linux 5.3.

  [Regression potential]
  The same test is being ignored right now, we risk ignoring a failure on an older version of linux, like 4.15. However, that could happen because the feature is backported to said kernel. And we are currently ignoring the failure anyway.

  ======================================

  
  https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac/autopkgtest-cosmic-canonical-kernel-team-bootstrap/cosmic/arm64/g/glibc/20180510_173125_32961@/log.gz

  FAIL: misc/tst-preadvwritev2
  original exit status 1
  error: tst-preadvwritev2-common.c:45: preadv2 did not fail with an invalid flag
  error: 1 test failures
  ----------
  ----------
  FAIL: misc/tst-preadvwritev64v2
  original exit status 1
  error: tst-preadvwritev2-common.c:45: preadv2 did not fail with an invalid flag
  error: 1 test failures

  This is testing for the flag immediately after the last known flag.
  So, if it's 0x8, it's going to test for 0x10.

  The test snippet:

    int invalid_flag = RWF_SUPPORTED != 0 ? __builtin_clz (RWF_SUPPORTED) : 2;
    invalid_flag = 0x1 << ((sizeof (int) * CHAR_BIT) - invalid_flag);

    char buf[32];
    const struct iovec vec = { .iov_base = buf, .iov_len = sizeof (buf) };
    if (preadv2 (temp_fd, &vec, 1, 0, invalid_flag) != -1)
      FAIL_EXIT1 ("preadv2 did not fail with an invalid flag");

  However, linux 4.16 has introduced RWF_APPEND.

  commit e1fc742e14e01d84d9693c4aca4ab23da65811fb
  Author: Jürg Billeter <j at bitron.ch>
  Date:   Fri Sep 29 14:07:17 2017 +0200

      fs: add RWF_APPEND

  ---
  +/* per-IO O_APPEND */
  +#define RWF_APPEND     ((__force __kernel_rwf_t)0x00000010)
  +
   /* mask of flags supported by the kernel */
  -#define RWF_SUPPORTED  (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT)
  +#define RWF_SUPPORTED  (RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_NOWAIT |\
  +                        RWF_APPEND)

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