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glibc/misc/sys
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Joan Bruguera 33e03f9cd2 misc: Fix rare fortify crash on wchar funcs. [BZ 29030] 
If `__glibc_objsize (__o) == (size_t) -1` (i.e. `__o` is unknown size), fortify
checks should pass, and `__whatever_alias` should be called.

Previously, `__glibc_objsize (__o) == (size_t) -1` was explicitly checked, but
on commit a643f60c53, this was moved into `__glibc_safe_or_unknown_len`.

A comment says the -1 case should work as: "The -1 check is redundant because
since it implies that __glibc_safe_len_cond is true.". But this fails when:
* `__s > 1`
* `__osz == -1` (i.e. unknown size at compile time)
* `__l` is big enough
* `__l * __s <= __osz` can be folded to a constant
(I only found this to be true for `mbsrtowcs` and other functions in wchar2.h)

In this case `__l * __s <= __osz` is false, and `__whatever_chk_warn` will be
called by `__glibc_fortify` or `__glibc_fortify_n` and crash the program.

This commit adds the explicit `__osz == -1` check again.
moc crashes on startup due to this, see: https://bugs.archlinux.org/task/74041

Minimal test case (test.c):
    #include <wchar.h>

    int main (void)
    {
        const char *hw = "HelloWorld";
        mbsrtowcs (NULL, &hw, (size_t)-1, NULL);
        return 0;
    }

Build with:
    gcc -O2 -Wp,-D_FORTIFY_SOURCE=2 test.c -o test && ./test

Output:
    *** buffer overflow detected ***: terminated

Fixes: BZ #29030
Signed-off-by: Joan Bruguera <joanbrugueram@gmail.com>
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
2022-04-25 17:32:30 +05:30
..
auxv.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
cdefs.h misc: Fix rare fortify crash on wchar funcs. [BZ 29030] 2022-04-25 17:32:30 +05:30
dir.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
file.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
ioctl.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
mman.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
param.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
queue.h [BZ #5779] 2008-03-05 05:50:39 +00:00
select.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
single_threaded.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
syslog.h misc: syslog: Move SYSLOG_NAME to USE_MISC (BZ #16355) 2022-04-15 10:41:54 -03:00
sysmacros.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
uio.h Update copyright dates with scripts/update-copyrights 2022-01-01 11:40:24 -08:00
xattr.h Add some missing access function attributes 2022-03-10 05:56:33 +05:30