Messages in this thread | | | Date | Sat, 19 Apr 2014 19:14:00 -0400 | From | Neil Horman <> | Subject | Re: [PATCH] coredump: fix va_list corruption |
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On Sat, Apr 19, 2014 at 10:15:07AM -0700, Eric Dumazet wrote: > From: Eric Dumazet <edumazet@google.com> > > A va_list needs to be copied in case it needs to be used twice. > > Thanks to Hugh for debugging this issue, leading to various panics. > > Tested: > > lpq84:~# echo "|/foobar12345 %h %h %h %h %h %h %h %h %h %h %h %h %h %h % > h %h %h %h %h %h" >/proc/sys/kernel/core_pattern > > 'produce_core' is simply : main() { *(int *)0 = 1;} > > lpq84:~# ./produce_core > Segmentation fault (core dumped) > lpq84:~# dmesg | tail -1 > [ 614.352947] Core dump to |/foobar12345 lpq84 lpq84 lpq84 lpq84 lpq84 > lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 lpq84 > lpq84 lpq84 (null) pipe failed > > Notice the last argument was replaced by a NULL (we were lucky enough to > not crash, but do not try this on your production machine !) > > After fix : > > lpq83:~# echo "|/foobar12345 %h %h %h %h %h %h %h %h %h %h %h %h %h %h % > h %h %h %h %h %h" >/proc/sys/kernel/core_pattern > lpq83:~# ./produce_core > Segmentation fault > lpq83:~# dmesg | tail -1 > [ 740.800441] Core dump to |/foobar12345 lpq83 lpq83 lpq83 lpq83 lpq83 > lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 lpq83 > lpq83 lpq83 lpq83 pipe failed > > Fixes: 5fe9d8ca21cc ("coredump: cn_vprintf() has no reason to call vsnprintf() twice") > Signed-off-by: Eric Dumazet <edumazet@google.com> > Diagnosed-by: Hugh Dickins <hughd@google.com> > Cc: Oleg Nesterov <oleg@redhat.com> > Cc: Neil Horman <nhorman@tuxdriver.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: stable@vger.kernel.org # 3.11+ > --- > > Note: This patch applies cleanly to 3.11+ but might need some > adjustments for older linux kernels... > > fs/coredump.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/fs/coredump.c b/fs/coredump.c > index e3ad709a4232..0b2528fb640e 100644 > --- a/fs/coredump.c > +++ b/fs/coredump.c > @@ -73,10 +73,15 @@ static int expand_corename(struct core_name *cn, int size) > static int cn_vprintf(struct core_name *cn, const char *fmt, va_list arg) > { > int free, need; > + va_list arg_copy; > > again: > free = cn->size - cn->used; > - need = vsnprintf(cn->corename + cn->used, free, fmt, arg); > + > + va_copy(arg_copy, arg); > + need = vsnprintf(cn->corename + cn->used, free, fmt, arg_copy); > + va_end(arg_copy); > + > if (need < free) { > cn->used += need; > return 0; > > >
Thanks Eric! Acked-by: Neil Horman <nhorman@tuxdriver.com>
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