2022-12-14 22:22:31

by Mathieu Desnoyers

Subject: [RFC PATCH] futex: Fix futex_waitv() hrtimer debug object leak on kcalloc error

In a scenario where kcalloc() fails to allocate memory, the futex_waitv
system call immediately returns -ENOMEM without invoking
destroy_hrtimer_on_stack(). When CONFIG_DEBUG_OBJECTS_TIMERS=y, this
results in leaking a timer debug object.

Fixes: bf69bad38cf6 ("futex: Implement sys_futex_waitv()")
Signed-off-by: Mathieu Desnoyers <[email protected]>
Cc: Andre Almeida <[email protected]>
Cc: Peter Zijlstra (Intel) <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Darren Hart <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: [email protected] # v5.16+
---
kernel/futex/syscalls.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/futex/syscalls.c b/kernel/futex/syscalls.c
index 086a22d1adb7..a8074079b09e 100644
--- a/kernel/futex/syscalls.c
+++ b/kernel/futex/syscalls.c
@@ -286,19 +286,22 @@ SYSCALL_DEFINE5(futex_waitv, struct futex_waitv __user *, waiters,
}

futexv = kcalloc(nr_futexes, sizeof(*futexv), GFP_KERNEL);
- if (!futexv)
- return -ENOMEM;
+ if (!futexv) {
+ ret = -ENOMEM;
+ goto destroy_timer;
+ }

ret = futex_parse_waitv(futexv, waiters, nr_futexes);
if (!ret)
ret = futex_wait_multiple(futexv, nr_futexes, timeout ? &to : NULL);

+ kfree(futexv);
+
+destroy_timer:
if (timeout) {
hrtimer_cancel(&to.timer);
destroy_hrtimer_on_stack(&to.timer);
}
-
- kfree(futexv);
return ret;
}

--
2.25.1

2022-12-15 21:23:22

by Davidlohr Bueso

Subject: Re: [RFC PATCH] futex: Fix futex_waitv() hrtimer debug object leak on kcalloc error

On Wed, 14 Dec 2022, Mathieu Desnoyers wrote:

>In a scenario where kcalloc() fails to allocate memory, the futex_waitv
>system call immediately returns -ENOMEM without invoking
>destroy_hrtimer_on_stack(). When CONFIG_DEBUG_OBJECTS_TIMERS=y, this
>results in leaking a timer debug object.
>
>Fixes: bf69bad38cf6 ("futex: Implement sys_futex_waitv()")
>Signed-off-by: Mathieu Desnoyers <[email protected]>
>Cc: Andre Almeida <[email protected]>
>Cc: Peter Zijlstra (Intel) <[email protected]>
>Cc: Thomas Gleixner <[email protected]>
>Cc: Ingo Molnar <[email protected]>
>Cc: Darren Hart <[email protected]>
>Cc: Davidlohr Bueso <[email protected]>
>Cc: [email protected] # v5.16+

Reviewed-by: Davidlohr Bueso <[email protected]>

2022-12-27 12:11:05

by tip-bot2 for Alexey Makhalov

Subject: [tip: locking/urgent] futex: Fix futex_waitv() hrtimer debug object leak on kcalloc error

The following commit has been merged into the locking/urgent branch of tip:

Commit-ID: 94cd8fa09f5f1ebdd4e90964b08b7f2cc4b36c43
Gitweb: https://git.kernel.org/tip/94cd8fa09f5f1ebdd4e90964b08b7f2cc4b36c43
Author: Mathieu Desnoyers <[email protected]>
AuthorDate: Wed, 14 Dec 2022 17:20:08 -05:00
Committer: Peter Zijlstra <[email protected]>
CommitterDate: Tue, 27 Dec 2022 12:52:02 +01:00

futex: Fix futex_waitv() hrtimer debug object leak on kcalloc error

In a scenario where kcalloc() fails to allocate memory, the futex_waitv
system call immediately returns -ENOMEM without invoking
destroy_hrtimer_on_stack(). When CONFIG_DEBUG_OBJECTS_TIMERS=y, this
results in leaking a timer debug object.

Fixes: bf69bad38cf6 ("futex: Implement sys_futex_waitv()")
Signed-off-by: Mathieu Desnoyers <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Davidlohr Bueso <[email protected]>
Cc: [email protected]
Cc: [email protected] # v5.16+
Link: https://lore.kernel.org/r/[email protected]
---
kernel/futex/syscalls.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/futex/syscalls.c b/kernel/futex/syscalls.c
index 086a22d..a807407 100644
--- a/kernel/futex/syscalls.c
+++ b/kernel/futex/syscalls.c
@@ -286,19 +286,22 @@ SYSCALL_DEFINE5(futex_waitv, struct futex_waitv __user *, waiters,
}

futexv = kcalloc(nr_futexes, sizeof(*futexv), GFP_KERNEL);
- if (!futexv)
- return -ENOMEM;
+ if (!futexv) {
+ ret = -ENOMEM;
+ goto destroy_timer;
+ }

ret = futex_parse_waitv(futexv, waiters, nr_futexes);
if (!ret)
ret = futex_wait_multiple(futexv, nr_futexes, timeout ? &to : NULL);

+ kfree(futexv);
+
+destroy_timer:
if (timeout) {
hrtimer_cancel(&to.timer);
destroy_hrtimer_on_stack(&to.timer);
}
-
- kfree(futexv);
return ret;
}