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[Bug nptl/3317] New: Overriding free which clobbers data and calls pthread_getspecific can get bad value
- From: "ian at airs dot com" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sources dot redhat dot com
- Date: 7 Oct 2006 01:38:16 -0000
- Subject: [Bug nptl/3317] New: Overriding free which clobbers data and calls pthread_getspecific can get bad value
- Reply-to: sourceware-bugzilla at sourceware dot org
If I override the libc free() function, and change that function to clobber some
bytes of the data, and then call pthread_getspecific from that function,
pthread_getspecific can return bad data. This is because __nptl_deallocate_tsd
frees data before clearing the pointer to that data. This happens around line 185:
/* The first block is allocated as part of the thread
THREAD_SETMEM_NC (self, specific, cnt, NULL);
The order of those lines should be reversed.
I first noticed this bug in linuxthreads, and then discovered that NPTL had the
same bug. I will file a separate bug against linuxthreads.
I will attach a test case which shows the problem on i686-pc-linux-gnu using
Fedora Core 4 with glibc-2.3.6-3.
Summary: Overriding free which clobbers data and calls
pthread_getspecific can get bad value
AssignedTo: drepper at redhat dot com
ReportedBy: ian at airs dot com
CC: glibc-bugs at sources dot redhat dot com
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