src/patches/glibc-2.38/0031-sysdeps-sem_open-Clear-O_CREAT-when-semaphore-file-i.patch

   1 From 63dbbc5c52f9823f86270f32fce20d1e91cdf484 Mon Sep 17 00:00:00 2001
   2 From: Sergio Durigan Junior <sergiodj@sergiodj.net>
   3 Date: Wed, 1 Nov 2023 18:15:23 -0400
   4 Subject: [PATCH 31/44] sysdeps: sem_open: Clear O_CREAT when semaphore file is
   5  expected to exist [BZ #30789]
   6
   7 When invoking sem_open with O_CREAT as one of its flags, we'll end up
   8 in the second part of sem_open's "if ((oflag & O_CREAT) == 0 || (oflag
   9 & O_EXCL) == 0)", which means that we don't expect the semaphore file
  10 to exist.
  11
  12 In that part, open_flags is initialized as "O_RDWR | O_CREAT | O_EXCL
  13 | O_CLOEXEC" and there's an attempt to open(2) the file, which will
  14 likely fail because it won't exist.  After that first (expected)
  15 failure, some cleanup is done and we go back to the label "try_again",
  16 which lives in the first part of the aforementioned "if".
  17
  18 The problem is that, in that part of the code, we expect the semaphore
  19 file to exist, and as such O_CREAT (this time the flag we pass to
  20 open(2)) needs to be cleaned from open_flags, otherwise we'll see
  21 another failure (this time unexpected) when trying to open the file,
  22 which will lead the call to sem_open to fail as well.
  23
  24 This can cause very strange bugs, especially with OpenMPI, which makes
  25 extensive use of semaphores.
  26
  27 Fix the bug by simplifying the logic when choosing open(2) flags and
  28 making sure O_CREAT is not set when the semaphore file is expected to
  29 exist.
  30
  31 A regression test for this issue would require a complex and cpu time
  32 consuming logic, since to trigger the wrong code path is not
  33 straightforward due the racy condition.  There is a somewhat reliable
  34 reproducer in the bug, but it requires using OpenMPI.
  35
  36 This resolves BZ #30789.
  37
  38 See also: https://bugs.launchpad.net/ubuntu/+source/h5py/+bug/2031912
  39
  40 Signed-off-by: Sergio Durigan Junior <sergiodj@sergiodj.net>
  41 Co-Authored-By: Simon Chopin <simon.chopin@canonical.com>
  42 Co-Authored-By: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
  43 Fixes: 533deafbdf189f5fbb280c28562dd43ace2f4b0f ("Use O_CLOEXEC in more places (BZ #15722)")
  44 (cherry picked from commit f957f47df75b9fab995754011491edebc6feb147)
  45 ---
  46  NEWS                       |  2 ++
  47  sysdeps/pthread/sem_open.c | 10 ++++------
  48  2 files changed, 6 insertions(+), 6 deletions(-)
  49
  50 diff --git a/NEWS b/NEWS
  51 index f117874e34..5ac488bf9b 100644
  52 --- a/NEWS
  53 +++ b/NEWS
  54 @@ -32,6 +32,8 @@ Security related changes:
  55  The following bugs are resolved with this release:
  56
  57    [30723] posix_memalign repeatedly scans long bin lists
  58 +  [30789] sem_open will fail on multithreaded scenarios when semaphore
  59 +    file doesn't exist (O_CREAT)
  60    [30804] F_GETLK, F_SETLK, and F_SETLKW value change for powerpc64 with
  61      -D_FILE_OFFSET_BITS=64
  62    [30842] Stack read overflow in getaddrinfo in no-aaaa mode (CVE-2023-4527)
  63 diff --git a/sysdeps/pthread/sem_open.c b/sysdeps/pthread/sem_open.c
  64 index e5db929d20..0e331a7445 100644
  65 --- a/sysdeps/pthread/sem_open.c
  66 +++ b/sysdeps/pthread/sem_open.c
  67 @@ -32,11 +32,12 @@
  68  # define __unlink unlink
  69  #endif
  70
  71 +#define SEM_OPEN_FLAGS (O_RDWR | O_NOFOLLOW | O_CLOEXEC)
  72 +
  73  sem_t *
  74  __sem_open (const char *name, int oflag, ...)
  75  {
  76    int fd;
  77 -  int open_flags;
  78    sem_t *result;
  79
  80    /* Check that shared futexes are supported.  */
  81 @@ -65,10 +66,8 @@ __sem_open (const char *name, int oflag, ...)
  82    /* If the semaphore object has to exist simply open it.  */
  83    if ((oflag & O_CREAT) == 0 || (oflag & O_EXCL) == 0)
  84      {
  85 -      open_flags = O_RDWR | O_NOFOLLOW | O_CLOEXEC;
  86 -      open_flags |= (oflag & ~(O_CREAT|O_ACCMODE));
  87      try_again:
  88 -      fd = __open (dirname.name, open_flags);
  89 +      fd = __open (dirname.name, (oflag & O_EXCL) | SEM_OPEN_FLAGS);
  90
  91        if (fd == -1)
  92         {
  93 @@ -135,8 +134,7 @@ __sem_open (const char *name, int oflag, ...)
  94             }
  95
  96           /* Open the file.  Make sure we do not overwrite anything.  */
  97 -         open_flags = O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC;
  98 -         fd = __open (tmpfname, open_flags, mode);
  99 +         fd = __open (tmpfname, O_CREAT | O_EXCL | SEM_OPEN_FLAGS, mode);
 100           if (fd == -1)
 101             {
 102               if (errno == EEXIST)
 103 --
 104 2.39.2
 105