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From: "batneil at thebatcave dot org dot uk" <sourceware-bugzilla@sourceware.org> To: glibc-bugs@sources.redhat.com Subject: [Bug nptl/2644] New: Race condition during unwind code after thread cancellation Date: Sun, 07 May 2006 13:56:00 -0000 [thread overview] Message-ID: <20060507135630.2644.batneil@thebatcave.org.uk> (raw) I think there is a race condition in the code in nptl/sysdeps/pthread/unwind-forcedunwind.c which can lead to a segfault. I found this in a redhat build, but it exists in CVS glibc too (as of May 6 2006). Consider a call to _Unwind_ForcedUnwind, when libgcc_s_forcedunwind has not been loaded. _Unwind_ForcedUnwind checks the value against null, and jumps to pthread_cancel_init. Meanwhile another thread comes in and initialises all these pointers, so the first check in pthread_cancel_init shows that libgcc_s_getcfa is non-null, so we return to _Unwind_ForcedUnwind and execute libgcc_s_forcedunwind. As the function pointer libgcc_s_forcedunwind has not been marked volatile, the compiler does not need to reload this value, and attempts to call the address it previously loaded, ie. 0. I have a test case which shows the problem and patch which I believe fixes it. -- Summary: Race condition during unwind code after thread cancellation Product: glibc Version: unspecified Status: NEW Severity: normal Priority: P2 Component: nptl AssignedTo: drepper at redhat dot com ReportedBy: batneil at thebatcave dot org dot uk CC: glibc-bugs at sources dot redhat dot com GCC build triplet: i686-redhat-linux GCC host triplet: i686-redhat-linux GCC target triplet: i686-redhat-linux http://sourceware.org/bugzilla/show_bug.cgi?id=2644 ------- You are receiving this mail because: ------- You are on the CC list for the bug, or are watching someone who is.
next reply other threads:[~2006-05-07 13:56 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2006-05-07 13:56 batneil at thebatcave dot org dot uk [this message] 2006-05-07 14:02 ` [Bug nptl/2644] " batneil at thebatcave dot org dot uk 2006-05-07 14:05 ` batneil at thebatcave dot org dot uk 2006-05-07 14:14 ` batneil at thebatcave dot org dot uk 2006-05-07 17:33 ` drepper at redhat dot com 2006-05-07 18:37 ` batneil at thebatcave dot org dot uk 2006-05-07 22:15 ` batneil at thebatcave dot org dot uk 2006-05-07 22:19 ` batneil at thebatcave dot org dot uk 2006-05-08 1:00 ` drepper at redhat dot com 2006-05-08 9:36 ` batneil at thebatcave dot org dot uk 2006-05-08 11:28 ` jakub at redhat dot com 2006-11-28 10:31 ` jakub at redhat dot com
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