From: Eric Dumazet <[email protected]>
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 <[email protected]>
Diagnosed-by: Hugh Dickins <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Neil Horman <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: [email protected] # 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;
On 04/19, Eric Dumazet wrote:
>
> A va_list needs to be copied in case it needs to be used twice.
OOPS :/
> --- 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);
> +
Thanks!
Acked-by: Oleg Nesterov <[email protected]>
On Sat, Apr 19, 2014 at 10:15:07AM -0700, Eric Dumazet wrote:
> From: Eric Dumazet <[email protected]>
>
> 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 <[email protected]>
> Diagnosed-by: Hugh Dickins <[email protected]>
> Cc: Oleg Nesterov <[email protected]>
> Cc: Neil Horman <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: [email protected] # 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 <[email protected]>