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Chris Metcalf wrote:
> I was doing some work in ld.so and was bit by this nasty little bug.
> Someone declared the "char*" variable that holds the temporary page
> mmap'ed to hold the _dl_dprintf buffer as "static". The result is that
> if two threads are in ld.so at once, they'll try to share this buffer,
> sort of, until one of them munmap's it and the other one crashes. It
> should just be a regular "auto" variable. Diff is against a recent git
> download.
>
> --- /u/cmetcalf/uClibc/ldso/ldso/dl-elf.c~ 2009-12-08 15:49:20.695835000
> -0500
> +++ /u/cmetcalf/uClibc/ldso/ldso/dl-elf.c 2009-12-16 13:44:16.032182000
> -0500
> @@ -887,21 +887,21 @@
> /* Minimal printf which handles only %s, %d, and %x */
> void _dl_dprintf(int fd, const char *fmt, ...)
> {
> #if __WORDSIZE > 32
> long int num;
> #else
> int num;
> #endif
> va_list args;
> char *start, *ptr, *string;
> - static char *buf;
> + char *buf;
>
> if (!fmt)
> return;
>
> buf = _dl_mmap((void *) 0, _dl_pagesize, PROT_READ | PROT_WRITE,
> MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> if (_dl_mmap_check_error(buf)) {
> _dl_write(fd, "mmap of a spare page failed!\n", 29);
> _dl_exit(20);
> }
>
>
Hi Chris,
the explanation is definitely clear and the fix is fine to me.
Could you provide the patch using git-format-patch to that it can be simply
committed with git-am ?... otherwise I can manage to do it on behalf of you.
thanks,
Carmelo
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