futex: Fix handling of bad requeue syscall pairing
PATCH 1/1 futex: Fix handling of bad requeue syscall pairing
From: Darren Hart <[email protected]>
If futex_requeue(requeue_pi=1) finds a futex_q that was created by a call other than futex_wait_requeue_pi(), the q.rt_waiter will be null. If so, this will result in an oops from the following call graph:
futex_requeue()
rt_mutex_start_proxy_lock()
task_blocks_on_rt_mutex()
waiter->task dereference
OOPSWe currently WARN_ON() if this is detected, clearly this is inadequate. If we detect a mis-pairing in futex_requeue(), bail out, sending -EINVAL to user-space.
---
kernel/futex.c | 11 +++++++++--
1 files changed, 9 insertions(+), 2 deletions(-)
kernel/futex.c +0 -0
@@ -1306,8 +1306,15 @@ retry_private:
if (!match_futex(&this->key, &key1)) continue;
- WARN_ON(!requeue_pi && this->rt_waiter);
- WARN_ON(requeue_pi && !this->rt_waiter);
+ /*
+ * FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always
+ * be paired with each other and no other futex ops.
+ */
+ if (requeue_pi && !this->rt_waiter ||
+ !requeue_pi && this->rt_waiter) {
+ ret = -EINVAL;
+ break;
+ }
/* * Wake nr_wake waiters. For requeue_pi, if we acquired the
Signature · 3 lines
Darren Hart IBM Linux Technology Center Real-Time Linux Team
PATCH v2 1/1 futex: Fix handling of bad requeue syscall pairing
From: Darren Hart <[email protected]>
If futex_requeue(requeue_pi=1) finds a futex_q that was created by a call other the futex_wait_requeue_pi(), the q.rt_waiter may be null. If so, this will result in an oops from the following call graph:
futex_requeue()
rt_mutex_start_proxy_lock()
task_blocks_on_rt_mutex()
waiter->task dereference
OOPSWe currently WARN_ON() if this is detected, clearly this is inadequate. If we detect a mispairing in futex_requeue(), bail out, seding -EINVAL to user-space.
V2: Fix parenthesis warnings.
---
kernel/futex.c | 11 +++++++++--
1 files changed, 9 insertions(+), 2 deletions(-)
kernel/futex.c +0 -0
@@ -1306,8 +1306,15 @@ retry_private:
if (!match_futex(&this->key, &key1)) continue;
- WARN_ON(!requeue_pi && this->rt_waiter);
- WARN_ON(requeue_pi && !this->rt_waiter);
+ /*
+ * FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always
+ * be paired with each other and no other futex ops.
+ */
+ if ((requeue_pi && !this->rt_waiter) ||
+ (!requeue_pi && this->rt_waiter)) {
+ ret = -EINVAL;
+ break;
+ }
/* * Wake nr_wake waiters. For requeue_pi, if we acquired the
Signature · 3 lines
Darren Hart IBM Linux Technology Center Real-Time Linux Team
Quoted 12 lines · Darren Hart
From: Darren Hart <[email protected]>
If
futex_requeue(requeue_pi=1)finds afutex_qthat was created by a call other thefutex_wait_requeue_pi(), the q.rt_waiter may be null. If so, this will result in an oops from the following call graph:
futex_requeue()
rt_mutex_start_proxy_lock()task_blocks_on_rt_mutex() waiter->task dereference OOPS
Quoted 8 lines
We currently
WARN_ON()if this is detected, clearly this is inadequate. If we detect a mispairing infutex_requeue(), bail out, seding-EINVALto user-space.V2: Fix parenthesis warnings.
Signed-off-by Darren Hart <[email protected]>Cc Thomas Gleixner <[email protected]>
Quoted 33 lines
Cc Steven Rostedt <[email protected]>Cc Ingo Molnar <[email protected]>CC Eric Dumazet <[email protected]>CC Dinakar Guniguntala <[email protected]>CC John Stultz <[email protected]>---
kernel/futex.c | 11 +++++++++-- 1 files changed, 9 insertions(+), 2 deletions(-)kernel/futex.c +9
-2@@ -1306,8 +1306,15 @@ retry_private:if (!match_futex (&this->key, &key1))continue ; -WARN_ON (!requeue_pi && this->rt_waiter); -WARN_ON (requeue_pi && !this->rt_waiter); +/* +* FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always +* be paired with each other and no other futex ops. +*/ +if ((requeue_pi && !this->rt_waiter) || + (!requeue_pi && this->rt_waiter)) { + ret = -EINVAL ; +break ; + }/* * Wake nr_wake waiters. For requeue_pi, if we acquired the
Commit-ID: 392741e0a4e17c82e3978b7fcbf04291294dc0a1 Gitweb: http://git.kernel.org/tip/392741e0a4e17c82e3978b7fcbf04291294dc0a1 Author: Darren Hart <[email protected]> AuthorDate: Fri, 7 Aug 2009 15:20:48 -0700 Committer: Ingo Molnar <[email protected]> CommitDate: Mon, 10 Aug 2009 20:38:11 +0200
futex: Fix handling of bad requeue syscall pairing
If futex_requeue(requeue_pi=1) finds a futex_q that was created by a call other the futex_wait_requeue_pi(), the q.rt_waiter may be null. If so, this will result in an oops from the following call graph:
futex_requeue()
rt_mutex_start_proxy_lock()
task_blocks_on_rt_mutex()
waiter->task dereference
OOPSWe currently WARN_ON() if this is detected, clearly this is inadequate. If we detect a mispairing in futex_requeue(), bail out, seding -EINVAL to user-space.
V2: Fix parenthesis warnings.
LKML-Reference: <[email protected]>
--- kernel/futex.c | 11 +++++++++-- 1 files changed, 9 insertions(+), 2 deletions(-)
kernel/futex.c +9 -2
@@ -1256,8 +1256,15 @@ retry_private:if (!match_futex (&this->key, &key1))continue ; -WARN_ON (!requeue_pi && this->rt_waiter); -WARN_ON (requeue_pi && !this->rt_waiter); +/* +* FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always +* be paired with each other and no other futex ops. +*/ +if ((requeue_pi && !this->rt_waiter) || + (!requeue_pi && this->rt_waiter)) { + ret = -EINVAL ; +break ; + }/* * Wake nr_wake waiters. For requeue_pi, if we acquired the