fix segfault in getitimer when old argument is NULL

Submitted by zhuyan (M) on Jan. 12, 2021, 7:56 a.m.

Details

Message ID c7c54510e4b94f5c9105b565b28560f4@huawei.com
State New
Series "fix segfault in getitimer when old argument is NULL"
Headers show

Commit Message

zhuyan (M) Jan. 12, 2021, 7:56 a.m.
When old is NULL, call old->it_interval.tv_sec to dereference a null pointer in getitimer.

The commit 558c01338b0b635632e70af6ec8a484ca70b0328 introduces this problem.

Signed-off-by: Qing Wu <wuqing30@huawei.com>
Signed-off-by: Yan Zhu <zhuyan34@huawei.com>
---
 src/signal/getitimer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--
2.12.3

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diff --git a/src/signal/getitimer.c b/src/signal/getitimer.c index 36d1eb9d..f6fde204 100644
--- a/src/signal/getitimer.c
+++ b/src/signal/getitimer.c
@@ -6,7 +6,7 @@  int getitimer(int which, struct itimerval *old)
 	if (sizeof(time_t) > sizeof(long)) {
 		long old32[4];
 		int r = __syscall(SYS_getitimer, which, old32);
-		if (!r) {
+		if (!r && old) {
 			old->it_interval.tv_sec = old32[0];
 			old->it_interval.tv_usec = old32[1];
 			old->it_value.tv_sec = old32[2];

Comments

Fangrui Song Jan. 12, 2021, 8:58 a.m.
On Mon, Jan 11, 2021 at 11:57 PM zhuyan (M) <zhuyan34@huawei.com> wrote:
>
>
> When old is NULL, call old->it_interval.tv_sec to dereference a null pointer in getitimer.
>
> The commit 558c01338b0b635632e70af6ec8a484ca70b0328 introduces this problem.
>
> Signed-off-by: Qing Wu <wuqing30@huawei.com>
> Signed-off-by: Yan Zhu <zhuyan34@huawei.com>
> ---
>  src/signal/getitimer.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/src/signal/getitimer.c b/src/signal/getitimer.c index 36d1eb9d..f6fde204 100644
> --- a/src/signal/getitimer.c
> +++ b/src/signal/getitimer.c
> @@ -6,7 +6,7 @@ int getitimer(int which, struct itimerval *old)
>         if (sizeof(time_t) > sizeof(long)) {
>                 long old32[4];
>                 int r = __syscall(SYS_getitimer, which, old32);
> -               if (!r) {
> +               if (!r && old) {
>                         old->it_interval.tv_sec = old32[0];
>                         old->it_interval.tv_usec = old32[1];
>                         old->it_value.tv_sec = old32[2];
> --
> 2.12.3
>

Null old is not sensible. POSIX and the Linux manpage say "The
getitimer() function shall store the current value of the timer
specified by which into the structure pointed to by value."
NULL is not a valid structure. musl does not need to work around
application bugs.