* [PATCH] futex: Don't enable IRQs unconditionally in put_pi_state()
@ 2020-11-06 8:52 Dan Carpenter
2020-11-09 11:21 ` Peter Zijlstra
2020-11-09 13:34 ` [tip: locking/urgent] " tip-bot2 for Dan Carpenter
0 siblings, 2 replies; 3+ messages in thread
From: Dan Carpenter @ 2020-11-06 8:52 UTC (permalink / raw)
To: Peter Zijlstra, Thomas Gleixner
Cc: Ingo Molnar, Darren Hart, linux-kernel, kernel-janitors
The exit_pi_state_list() function calls put_pi_state() with IRQs
disabled and is not expecting that IRQs will be enabled inside the
function. Use the _irqsave() so that IRQs are restored to the original
state instead of enabled unconditionally.
Fixes: 153fbd1226fb ("futex: Fix more put_pi_state() vs. exit_pi_state_list() races")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
This is from static analysis and not tested. I am not very familiar
with futex code.
kernel/futex.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c
index f8614ef4ff31..ca84745713bc 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -788,8 +788,9 @@ static void put_pi_state(struct futex_pi_state *pi_state)
*/
if (pi_state->owner) {
struct task_struct *owner;
+ unsigned long flags;
- raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
+ raw_spin_lock_irqsave(&pi_state->pi_mutex.wait_lock, flags);
owner = pi_state->owner;
if (owner) {
raw_spin_lock(&owner->pi_lock);
@@ -797,7 +798,7 @@ static void put_pi_state(struct futex_pi_state *pi_state)
raw_spin_unlock(&owner->pi_lock);
}
rt_mutex_proxy_unlock(&pi_state->pi_mutex, owner);
- raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
+ raw_spin_unlock_irqrestore(&pi_state->pi_mutex.wait_lock, flags);
}
if (current->pi_state_cache) {
--
2.28.0
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] futex: Don't enable IRQs unconditionally in put_pi_state()
2020-11-06 8:52 [PATCH] futex: Don't enable IRQs unconditionally in put_pi_state() Dan Carpenter
@ 2020-11-09 11:21 ` Peter Zijlstra
2020-11-09 13:34 ` [tip: locking/urgent] " tip-bot2 for Dan Carpenter
1 sibling, 0 replies; 3+ messages in thread
From: Peter Zijlstra @ 2020-11-09 11:21 UTC (permalink / raw)
To: Dan Carpenter
Cc: Thomas Gleixner, Ingo Molnar, Darren Hart, linux-kernel, kernel-janitors
On Fri, Nov 06, 2020 at 11:52:05AM +0300, Dan Carpenter wrote:
> The exit_pi_state_list() function calls put_pi_state() with IRQs
> disabled and is not expecting that IRQs will be enabled inside the
> function. Use the _irqsave() so that IRQs are restored to the original
> state instead of enabled unconditionally.
>
> Fixes: 153fbd1226fb ("futex: Fix more put_pi_state() vs. exit_pi_state_list() races")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> This is from static analysis and not tested. I am not very familiar
> with futex code.
It it exceedingly rare if at all possible to trigger this, but yes, your
patch is correct.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>
> kernel/futex.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/futex.c b/kernel/futex.c
> index f8614ef4ff31..ca84745713bc 100644
> --- a/kernel/futex.c
> +++ b/kernel/futex.c
> @@ -788,8 +788,9 @@ static void put_pi_state(struct futex_pi_state *pi_state)
> */
> if (pi_state->owner) {
> struct task_struct *owner;
> + unsigned long flags;
>
> - raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
> + raw_spin_lock_irqsave(&pi_state->pi_mutex.wait_lock, flags);
> owner = pi_state->owner;
> if (owner) {
> raw_spin_lock(&owner->pi_lock);
> @@ -797,7 +798,7 @@ static void put_pi_state(struct futex_pi_state *pi_state)
> raw_spin_unlock(&owner->pi_lock);
> }
> rt_mutex_proxy_unlock(&pi_state->pi_mutex, owner);
> - raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
> + raw_spin_unlock_irqrestore(&pi_state->pi_mutex.wait_lock, flags);
> }
>
> if (current->pi_state_cache) {
> --
> 2.28.0
>
^ permalink raw reply [flat|nested] 3+ messages in thread* [tip: locking/urgent] futex: Don't enable IRQs unconditionally in put_pi_state()
2020-11-06 8:52 [PATCH] futex: Don't enable IRQs unconditionally in put_pi_state() Dan Carpenter
2020-11-09 11:21 ` Peter Zijlstra
@ 2020-11-09 13:34 ` tip-bot2 for Dan Carpenter
1 sibling, 0 replies; 3+ messages in thread
From: tip-bot2 for Dan Carpenter @ 2020-11-09 13:34 UTC (permalink / raw)
To: linux-tip-commits
Cc: Dan Carpenter, Thomas Gleixner, Peter Zijlstra (Intel),
stable, x86, linux-kernel
The following commit has been merged into the locking/urgent branch of tip:
Commit-ID: 1e106aa3509b86738769775969822ffc1ec21bf4
Gitweb: https://git.kernel.org/tip/1e106aa3509b86738769775969822ffc1ec21bf4
Author: Dan Carpenter <dan.carpenter@oracle.com>
AuthorDate: Fri, 06 Nov 2020 11:52:05 +03:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Mon, 09 Nov 2020 14:30:30 +01:00
futex: Don't enable IRQs unconditionally in put_pi_state()
The exit_pi_state_list() function calls put_pi_state() with IRQs disabled
and is not expecting that IRQs will be enabled inside the function.
Use the _irqsave() variant so that IRQs are restored to the original state
instead of being enabled unconditionally.
Fixes: 153fbd1226fb ("futex: Fix more put_pi_state() vs. exit_pi_state_list() races")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20201106085205.GA1159983@mwanda
---
kernel/futex.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c
index ac32887..00259c7 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -788,8 +788,9 @@ static void put_pi_state(struct futex_pi_state *pi_state)
*/
if (pi_state->owner) {
struct task_struct *owner;
+ unsigned long flags;
- raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
+ raw_spin_lock_irqsave(&pi_state->pi_mutex.wait_lock, flags);
owner = pi_state->owner;
if (owner) {
raw_spin_lock(&owner->pi_lock);
@@ -797,7 +798,7 @@ static void put_pi_state(struct futex_pi_state *pi_state)
raw_spin_unlock(&owner->pi_lock);
}
rt_mutex_proxy_unlock(&pi_state->pi_mutex, owner);
- raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
+ raw_spin_unlock_irqrestore(&pi_state->pi_mutex.wait_lock, flags);
}
if (current->pi_state_cache) {
^ permalink raw reply related [flat|nested] 3+ messages in thread
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2020-11-06 8:52 [PATCH] futex: Don't enable IRQs unconditionally in put_pi_state() Dan Carpenter
2020-11-09 11:21 ` Peter Zijlstra
2020-11-09 13:34 ` [tip: locking/urgent] " tip-bot2 for Dan Carpenter
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