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Re: SIGSEGV in *__GI_putwc (wc=84, fp=0x804b040) at putwc.c:31


On Mon, 2004-06-21 at 23:13, Martin Schlemmer wrote:
> Hi
> 
> We have a sandbox that verify that all writes stay in the sandbox.
> 

BTW, this is GPL, and available if somebody interested.

> With cvs 20040619 (and prob earlier?) of glibc the libio/tst_putwc
> keeps on segfaulting during 'make check'.  Trace follows:
> 
> ---
> Program received signal SIGSEGV, Segmentation fault.
> 0x4005ec9f in *__GI_putwc (wc=84, fp=0x804b040) at putwc.c:31
> 31        result = _IO_putwc_unlocked (wc, fp);
> (gdb) bt
> #0  0x4005ec9f in *__GI_putwc (wc=84, fp=0x804b040) at putwc.c:31
> #1  0x08049145 in do_test ()
> #2  0x0804b040 in ?? ()
> #3  0x00000001 in ?? ()
> #4  0x00000000 in ?? ()
> #5  0x00000001 in ?? ()
> #6  0xffffffff in ?? ()
> #7  0x4011385c in __elf_set___libc_thread_subfreeres_element___rpc_thread_destroy__ ()
>    from /space/var/tmp/portage/glibc-2.3.4.20040619/work/build/libc.so.6
> #8  0xbfffda08 in ?? ()
> #9  0x4011385c in __elf_set___libc_thread_subfreeres_element___rpc_thread_destroy__ ()
>    from /space/var/tmp/portage/glibc-2.3.4.20040619/work/build/libc.so.6
> #10 0x00000000 in ?? ()
> #11 0x400b3e64 in *__GI___sbrk (increment=-1073751100) at ../sysdeps/generic/sbrk.c:34
> Previous frame inner to this frame (corrupt stack?)
> (gdb)
> ---
> 
> The whole glibc is compiled with -ggdb, so I assume the 'untraced' calls
> is from the libsandbox.so that gets preloaded.  Now:
> 
> 1)  Anybody seen anything like this before, or can think of anything
> that might be related?  I guess it might be stack corruption on the
> side of libsandbox.so, but it have been working for months unchanged,
> and this is pretty much the first of its kind.
> 
> 2)  If not 1), is there a way to get gdb to also trace into the
> preloaded libsandbox.so?
> 
> NB: Please keep me in CC
> 
> 
> Thanks,


-- 
Martin Schlemmer

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