glibc: backport patch to fix CVE-2023-4911
https://lwn.net/ml/oss-security/20231003175031.GA16924@localhost.localdomain/
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John
John Zimmermann
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cf00278026
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@ -0,0 +1,205 @@
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From: Siddhesh Poyarekar <siddhesh@sourceware.org>
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Subject: [committed 1/2] Propagate GLIBC_TUNABLES in setxid binaries
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Date: Tue, 3 Oct 2023 13:08:10 -0400
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GLIBC_TUNABLES scrubbing happens earlier than envvar scrubbing and some
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tunables are required to propagate past setxid boundary, like their
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env_alias. Rely on tunable scrubbing to clean out GLIBC_TUNABLES like
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before, restoring behaviour in glibc 2.37 and earlier.
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Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
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Reviewed-by: Carlos O'Donell <carlos@redhat.com>
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---
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sysdeps/generic/unsecvars.h | 1 -
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1 file changed, 1 deletion(-)
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diff --git a/sysdeps/generic/unsecvars.h b/sysdeps/generic/unsecvars.h
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index 81397fb90b..8278c50a84 100644
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--- a/sysdeps/generic/unsecvars.h
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+++ b/sysdeps/generic/unsecvars.h
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@@ -1,16 +1,9 @@
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-#if !HAVE_TUNABLES
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-# define GLIBC_TUNABLES_ENVVAR "GLIBC_TUNABLES\0"
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-#else
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-# define GLIBC_TUNABLES_ENVVAR
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-#endif
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-
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/* Environment variable to be removed for SUID programs. The names are
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all stuffed in a single string which means they have to be terminated
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with a '\0' explicitly. */
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#define UNSECURE_ENVVARS \
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"GCONV_PATH\0" \
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"GETCONF_DIR\0" \
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- GLIBC_TUNABLES_ENVVAR \
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"HOSTALIASES\0" \
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"LD_AUDIT\0" \
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"LD_DEBUG\0" \
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From: Siddhesh Poyarekar <siddhesh@sourceware.org>
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Subject: [committed 2/2] tunables: Terminate if end of input is reached
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(CVE-2023-4911)
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Date: Tue, 3 Oct 2023 13:08:11 -0400
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The string parsing routine may end up writing beyond bounds of tunestr
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if the input tunable string is malformed, of the form name=name=val.
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This gets processed twice, first as name=name=val and next as name=val,
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resulting in tunestr being name=name=val:name=val, thus overflowing
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tunestr.
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Terminate the parsing loop at the first instance itself so that tunestr
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does not overflow.
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This also fixes up tst-env-setuid-tunables to actually handle failures
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correct and add new tests to validate the fix for this CVE.
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Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
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Reviewed-by: Carlos O'Donell <carlos@redhat.com>
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---
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NEWS | 5 +++++
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elf/dl-tunables.c | 17 +++++++++-------
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elf/tst-env-setuid-tunables.c | 37 +++++++++++++++++++++++++++--------
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3 files changed, 44 insertions(+), 15 deletions(-)
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diff --git a/NEWS b/NEWS
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index a94650da64..cc4b81f0ac 100644
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--- a/NEWS
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+++ b/NEWS
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@@ -64,6 +64,11 @@ Security related changes:
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an application calls getaddrinfo for AF_INET6 with AI_CANONNAME,
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AI_ALL and AI_V4MAPPED flags set.
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+ CVE-2023-4911: If a tunable of the form NAME=NAME=VAL is passed in the
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+ environment of a setuid program and NAME is valid, it may result in a
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+ buffer overflow, which could be exploited to achieve escalated
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+ privileges. This flaw was introduced in glibc 2.34.
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+
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The following bugs are resolved with this release:
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[The release manager will add the list generated by
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diff --git a/elf/dl-tunables.c b/elf/dl-tunables.c
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index 62b7332d95..cae67efa0a 100644
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--- a/elf/dl-tunables.c
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+++ b/elf/dl-tunables.c
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@@ -180,11 +180,7 @@ parse_tunables (char *tunestr, char *valstring)
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/* If we reach the end of the string before getting a valid name-value
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pair, bail out. */
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if (p[len] == '\0')
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- {
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- if (__libc_enable_secure)
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- tunestr[off] = '\0';
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- return;
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- }
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+ break;
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/* We did not find a valid name-value pair before encountering the
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colon. */
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@@ -244,9 +240,16 @@ parse_tunables (char *tunestr, char *valstring)
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}
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}
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- if (p[len] != '\0')
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- p += len + 1;
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+ /* We reached the end while processing the tunable string. */
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+ if (p[len] == '\0')
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+ break;
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+
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+ p += len + 1;
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}
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+
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+ /* Terminate tunestr before we leave. */
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+ if (__libc_enable_secure)
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+ tunestr[off] = '\0';
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}
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/* Enable the glibc.malloc.check tunable in SETUID/SETGID programs only when
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diff --git a/elf/tst-env-setuid-tunables.c b/elf/tst-env-setuid-tunables.c
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index 7dfb0e073a..f0b92c97e7 100644
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--- a/elf/tst-env-setuid-tunables.c
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+++ b/elf/tst-env-setuid-tunables.c
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@@ -50,6 +50,8 @@ const char *teststrings[] =
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"glibc.malloc.perturb=0x800:not_valid.malloc.check=2:glibc.malloc.mmap_threshold=4096",
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"glibc.not_valid.check=2:glibc.malloc.mmap_threshold=4096",
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"not_valid.malloc.check=2:glibc.malloc.mmap_threshold=4096",
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+ "glibc.malloc.mmap_threshold=glibc.malloc.mmap_threshold=4096",
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+ "glibc.malloc.check=2",
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"glibc.malloc.garbage=2:glibc.maoc.mmap_threshold=4096:glibc.malloc.check=2",
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"glibc.malloc.check=4:glibc.malloc.garbage=2:glibc.maoc.mmap_threshold=4096",
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":glibc.malloc.garbage=2:glibc.malloc.check=1",
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@@ -68,6 +70,8 @@ const char *resultstrings[] =
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"glibc.malloc.perturb=0x800:glibc.malloc.mmap_threshold=4096",
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"glibc.malloc.mmap_threshold=4096",
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"glibc.malloc.mmap_threshold=4096",
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+ "glibc.malloc.mmap_threshold=glibc.malloc.mmap_threshold=4096",
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+ "",
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"",
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"",
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"",
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@@ -88,11 +88,18 @@ test_child (int off)
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const char *val = getenv ("GLIBC_TUNABLES");
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#if HAVE_TUNABLES
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+ printf (" [%d] GLIBC_TUNABLES is %s\n", off, val);
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+ fflush (stdout);
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if (val != NULL && strcmp (val, resultstrings[off]) == 0)
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return 0;
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if (val != NULL)
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- printf ("[%d] Unexpected GLIBC_TUNABLES VALUE %s\n", off, val);
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+ printf (" [%d] Unexpected GLIBC_TUNABLES VALUE %s, expected %s\n",
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+ off, val, resultstrings[off]);
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+ else
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+ printf (" [%d] GLIBC_TUNABLES environment variable absent\n", off);
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+
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+ fflush (stdout);
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return 1;
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#else
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@@ -106,21 +117,26 @@ do_test (int argc, char **argv)
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if (ret != 0)
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exit (1);
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- exit (EXIT_SUCCESS);
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+ /* Special return code to make sure that the child executed all the way
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+ through. */
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+ exit (42);
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}
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else
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{
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- int ret = 0;
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-
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/* Spawn tests. */
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for (int i = 0; i < array_length (teststrings); i++)
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{
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char buf[INT_BUFSIZE_BOUND (int)];
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- printf ("Spawned test for %s (%d)\n", teststrings[i], i);
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+ printf ("[%d] Spawned test for %s\n", i, teststrings[i]);
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snprintf (buf, sizeof (buf), "%d\n", i);
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+ fflush (stdout);
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if (setenv ("GLIBC_TUNABLES", teststrings[i], 1) != 0)
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- exit (1);
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+ {
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+ printf (" [%d] Failed to set GLIBC_TUNABLES: %m", i);
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+ support_record_failure ();
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+ continue;
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+ }
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int status = support_capture_subprogram_self_sgid (buf);
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@@ -128,9 +144,14 @@ do_test (int argc, char **argv)
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if (WEXITSTATUS (status) == EXIT_UNSUPPORTED)
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return EXIT_UNSUPPORTED;
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- ret |= status;
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+ if (WEXITSTATUS (status) != 42)
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+ {
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+ printf (" [%d] child failed with status %d\n", i,
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+ WEXITSTATUS (status));
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+ support_record_failure ();
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+ }
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}
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- return ret;
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+ return 0;
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}
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}
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@ -1,7 +1,7 @@
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# Template file for 'glibc'
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pkgname=glibc
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version=2.36
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revision=1
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revision=2
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_patchver="72-g0f90d6204d"
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bootstrap=yes
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short_desc="GNU C library"
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