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| author | Thomas Schoebel-Theuer <tst@1und1.de> | 2021-03-07 08:23:22 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-03-11 13:46:35 +0100 |
| commit | ad83307d1e625704cbf8e88de2c66dc8b175899e (patch) | |
| tree | 8524bb6d7eb1539b2da7555bce9abc755b4b2bef /kernel | |
| parent | d68eefc0f6050e64dc57aefc0638eac7bb441050 (diff) | |
| download | linux-stable-ad83307d1e625704cbf8e88de2c66dc8b175899e.tar.gz linux-stable-ad83307d1e625704cbf8e88de2c66dc8b175899e.tar.bz2 linux-stable-ad83307d1e625704cbf8e88de2c66dc8b175899e.zip | |
futex: fix spin_lock() / spin_unlock_irq() imbalance
This patch and problem analysis is specific for 4.4 LTS, due to incomplete
backporting of other fixes. Later LTS series have different backports.
The following is obviously incorrect:
static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this,
struct futex_hash_bucket *hb)
{
[...]
raw_spin_lock(&pi_state->pi_mutex.wait_lock);
[...]
raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
[...]
}
The 4.4-specific fix should probably go in the direction of
b4abf91047c,
making everything irq-safe.
Probably, backporting of b4abf91047c
to 4.4 LTS could thus be another good idea.
However, this might involve some more 4.4-specific work and
require thorough testing:
> git log --oneline v4.4..b4abf91047c -- kernel/futex.c kernel/locking/rtmutex.c | wc -l
10
So this patch is just an obvious quickfix for now.
Hint: the lock order is documented in 4.9.y and later. A similar
documenting is missing in 4.4.y. Please somebody either backport also,
or write a new description, if there would be some differences I cannot
easily see at the moment. Without reliable docs,
inspection of the locking correctness may become a pain.
Signed-off-by: Thomas Schoebel-Theuer <tst@1und1.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Lee Jones <lee.jones@linaro.org>
Fixes: 394fc4981426 ("futex: Rework inconsistent rt_mutex/futex_q state")
Fixes: 6510e4a2d04f ("futex,rt_mutex: Provide futex specific rt_mutex API")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/futex.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index 1ede3542819c..95cdc11c89f8 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1408,7 +1408,7 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this, if (pi_state->owner != current) return -EINVAL; - raw_spin_lock(&pi_state->pi_mutex.wait_lock); + raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock); new_owner = rt_mutex_next_owner(&pi_state->pi_mutex); /* |