| Message ID | 20241017151007.92215-1-thomas.hellstrom@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] locking/ww_mutex: Adjust to lockdep nest_lock requirements | expand |
On Thu, Oct 17, 2024 at 05:10:07PM +0200, Thomas Hellström wrote: > When using mutex_acquire_nest() with a nest_lock, lockdep refcounts the > number of acquired lockdep_maps of mutexes of the same class, and also > keeps a pointer to the first acquired lockdep_map of a class. That pointer > is then used for various comparison-, printing- and checking purposes, > but there is no mechanism to actively ensure that lockdep_map stays in > memory. Instead, a warning is printed if the lockdep_map is freed and > there are still held locks of the same lock class, even if the lockdep_map > itself has been released. > > In the context of WW/WD transactions that means that if a user unlocks > and frees a ww_mutex from within an ongoing ww transaction, and that > mutex happens to be the first ww_mutex grabbed in the transaction, > such a warning is printed and there might be a risk of a UAF. > > Note that this is only problem when lockdep is enabled and affects only > dereferences of struct lockdep_map. > > Adjust to this by adding a fake lockdep_map to the acquired context and > make sure it is the first acquired lockdep map of the associated > ww_mutex class. Then hold it for the duration of the WW/WD transaction. > > This has the side effect that trying to lock a ww mutex *without* a > ww_acquire_context but where a such context has been acquire, we'd see > a lockdep splat. The test-ww_mutex.c selftest attempts to do that, so > modify that particular test to not acquire a ww_acquire_context if it > is not going to be used. > > v2: > - Lower the number of locks in the test-ww_mutex > stress(STRESS_ALL) test to accommodate the dummy lock > introduced in this patch without overflowing lockdep held lock > references. > > v3: > - Adjust the ww_test_normal locking-api selftest to avoid > recursive locking (Boqun Feng) > - Initialize the dummy lock map with LD_WAIT_SLEEP to agree with > how the corresponding ww_mutex lockmaps are initialized > (Boqun Feng) > Thanks! > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Will Deacon <will@kernel.org> > Cc: Waiman Long <longman@redhat.com> > Cc: Boqun Feng <boqun.feng@gmail.com> > Cc: Maarten Lankhorst <maarten@lankhorst.se> > Cc: Christian König <christian.koenig@amd.com> > Cc: dri-devel@lists.freedesktop.org > Cc: linux-kernel@vger.kernel.org Feel free to use these tags if you need. Co-developed-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Boqun Feng <boqun.feng@gmail.com> > Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> > Acked-by: maarten.lankhorst@linux.intel.com #v1 Tested-by: Boqun Feng <boqun.feng@gmail.com> Peter, since the v2 of this is actually picked in tip/locking/core, I assume you are going to drop that pick this v3? Let me know how you want to proceed, since I have a PR based on tip/locking/core. Regards, Boqun > --- > include/linux/ww_mutex.h | 14 ++++++++++++++ > kernel/locking/test-ww_mutex.c | 8 +++++--- > lib/locking-selftest.c | 4 ++-- > 3 files changed, 21 insertions(+), 5 deletions(-) > > diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h > index bb763085479a..45ff6f7a872b 100644 > --- a/include/linux/ww_mutex.h > +++ b/include/linux/ww_mutex.h > @@ -65,6 +65,16 @@ struct ww_acquire_ctx { > #endif > #ifdef CONFIG_DEBUG_LOCK_ALLOC > struct lockdep_map dep_map; > + /** > + * @first_lock_dep_map: fake lockdep_map for first locked ww_mutex. > + * > + * lockdep requires the lockdep_map for the first locked ww_mutex > + * in a ww transaction to remain in memory until all ww_mutexes of > + * the transaction have been unlocked. Ensure this by keeping a > + * fake locked ww_mutex lockdep map between ww_acquire_init() and > + * ww_acquire_fini(). > + */ > + struct lockdep_map first_lock_dep_map; > #endif > #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH > unsigned int deadlock_inject_interval; > @@ -146,7 +156,10 @@ static inline void ww_acquire_init(struct ww_acquire_ctx *ctx, > debug_check_no_locks_freed((void *)ctx, sizeof(*ctx)); > lockdep_init_map(&ctx->dep_map, ww_class->acquire_name, > &ww_class->acquire_key, 0); > + lockdep_init_map_wait(&ctx->first_lock_dep_map, ww_class->mutex_name, > + &ww_class->mutex_key, 0, LD_WAIT_SLEEP); > mutex_acquire(&ctx->dep_map, 0, 0, _RET_IP_); > + mutex_acquire_nest(&ctx->first_lock_dep_map, 0, 0, &ctx->dep_map, _RET_IP_); > #endif > #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH > ctx->deadlock_inject_interval = 1; > @@ -185,6 +198,7 @@ static inline void ww_acquire_done(struct ww_acquire_ctx *ctx) > static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx) > { > #ifdef CONFIG_DEBUG_LOCK_ALLOC > + mutex_release(&ctx->first_lock_dep_map, _THIS_IP_); > mutex_release(&ctx->dep_map, _THIS_IP_); > #endif > #ifdef DEBUG_WW_MUTEXES > diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c > index 10a5736a21c2..5d58b2c0ef98 100644 > --- a/kernel/locking/test-ww_mutex.c > +++ b/kernel/locking/test-ww_mutex.c > @@ -62,7 +62,8 @@ static int __test_mutex(unsigned int flags) > int ret; > > ww_mutex_init(&mtx.mutex, &ww_class); > - ww_acquire_init(&ctx, &ww_class); > + if (flags & TEST_MTX_CTX) > + ww_acquire_init(&ctx, &ww_class); > > INIT_WORK_ONSTACK(&mtx.work, test_mutex_work); > init_completion(&mtx.ready); > @@ -90,7 +91,8 @@ static int __test_mutex(unsigned int flags) > ret = wait_for_completion_timeout(&mtx.done, TIMEOUT); > } > ww_mutex_unlock(&mtx.mutex); > - ww_acquire_fini(&ctx); > + if (flags & TEST_MTX_CTX) > + ww_acquire_fini(&ctx); > > if (ret) { > pr_err("%s(flags=%x): mutual exclusion failure\n", > @@ -679,7 +681,7 @@ static int __init test_ww_mutex_init(void) > if (ret) > return ret; > > - ret = stress(2047, hweight32(STRESS_ALL)*ncpus, STRESS_ALL); > + ret = stress(2046, hweight32(STRESS_ALL)*ncpus, STRESS_ALL); > if (ret) > return ret; > > diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c > index 6f6a5fc85b42..6750321e3e9a 100644 > --- a/lib/locking-selftest.c > +++ b/lib/locking-selftest.c > @@ -1720,8 +1720,6 @@ static void ww_test_normal(void) > { > int ret; > > - WWAI(&t); > - > /* > * None of the ww_mutex codepaths should be taken in the 'normal' > * mutex calls. The easiest way to verify this is by using the > @@ -1770,6 +1768,8 @@ static void ww_test_normal(void) > ww_mutex_base_unlock(&o.base); > WARN_ON(o.ctx != (void *)~0UL); > > + WWAI(&t); > + > /* nest_lock */ > o.ctx = (void *)~0UL; > ww_mutex_base_lock_nest_lock(&o.base, &t); > -- > 2.46.0 >
On Thu, 2024-10-17 at 09:13 -0700, Boqun Feng wrote: > On Thu, Oct 17, 2024 at 05:10:07PM +0200, Thomas Hellström wrote: > > When using mutex_acquire_nest() with a nest_lock, lockdep refcounts > > the > > number of acquired lockdep_maps of mutexes of the same class, and > > also > > keeps a pointer to the first acquired lockdep_map of a class. That > > pointer > > is then used for various comparison-, printing- and checking > > purposes, > > but there is no mechanism to actively ensure that lockdep_map stays > > in > > memory. Instead, a warning is printed if the lockdep_map is freed > > and > > there are still held locks of the same lock class, even if the > > lockdep_map > > itself has been released. > > > > In the context of WW/WD transactions that means that if a user > > unlocks > > and frees a ww_mutex from within an ongoing ww transaction, and > > that > > mutex happens to be the first ww_mutex grabbed in the transaction, > > such a warning is printed and there might be a risk of a UAF. > > > > Note that this is only problem when lockdep is enabled and affects > > only > > dereferences of struct lockdep_map. > > > > Adjust to this by adding a fake lockdep_map to the acquired context > > and > > make sure it is the first acquired lockdep map of the associated > > ww_mutex class. Then hold it for the duration of the WW/WD > > transaction. > > > > This has the side effect that trying to lock a ww mutex *without* a > > ww_acquire_context but where a such context has been acquire, we'd > > see > > a lockdep splat. The test-ww_mutex.c selftest attempts to do that, > > so > > modify that particular test to not acquire a ww_acquire_context if > > it > > is not going to be used. > > > > v2: > > - Lower the number of locks in the test-ww_mutex > > stress(STRESS_ALL) test to accommodate the dummy lock > > introduced in this patch without overflowing lockdep held lock > > references. > > > > v3: > > - Adjust the ww_test_normal locking-api selftest to avoid > > recursive locking (Boqun Feng) > > - Initialize the dummy lock map with LD_WAIT_SLEEP to agree with > > how the corresponding ww_mutex lockmaps are initialized > > (Boqun Feng) > > > > Thanks! > > > Cc: Peter Zijlstra <peterz@infradead.org> > > Cc: Ingo Molnar <mingo@redhat.com> > > Cc: Will Deacon <will@kernel.org> > > Cc: Waiman Long <longman@redhat.com> > > Cc: Boqun Feng <boqun.feng@gmail.com> > > Cc: Maarten Lankhorst <maarten@lankhorst.se> > > Cc: Christian König <christian.koenig@amd.com> > > Cc: dri-devel@lists.freedesktop.org > > Cc: linux-kernel@vger.kernel.org > > Feel free to use these tags if you need. > > Co-developed-by: Boqun Feng <boqun.feng@gmail.com> > Signed-off-by: Boqun Feng <boqun.feng@gmail.com> > > > Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> > > Acked-by: maarten.lankhorst@linux.intel.com #v1 > > Tested-by: Boqun Feng <boqun.feng@gmail.com> Peter, Can you add these 3 tags when picking, or do you want me to send a v4 with the tags included. Thanks, Thomas > > Peter, since the v2 of this is actually picked in tip/locking/core, I > assume you are going to drop that pick this v3? Let me know how you > want > to proceed, since I have a PR based on tip/locking/core. > > Regards, > Boqun > > > --- > > include/linux/ww_mutex.h | 14 ++++++++++++++ > > kernel/locking/test-ww_mutex.c | 8 +++++--- > > lib/locking-selftest.c | 4 ++-- > > 3 files changed, 21 insertions(+), 5 deletions(-) > > > > diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h > > index bb763085479a..45ff6f7a872b 100644 > > --- a/include/linux/ww_mutex.h > > +++ b/include/linux/ww_mutex.h > > @@ -65,6 +65,16 @@ struct ww_acquire_ctx { > > #endif > > #ifdef CONFIG_DEBUG_LOCK_ALLOC > > struct lockdep_map dep_map; > > + /** > > + * @first_lock_dep_map: fake lockdep_map for first locked > > ww_mutex. > > + * > > + * lockdep requires the lockdep_map for the first locked > > ww_mutex > > + * in a ww transaction to remain in memory until all > > ww_mutexes of > > + * the transaction have been unlocked. Ensure this by > > keeping a > > + * fake locked ww_mutex lockdep map between > > ww_acquire_init() and > > + * ww_acquire_fini(). > > + */ > > + struct lockdep_map first_lock_dep_map; > > #endif > > #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH > > unsigned int deadlock_inject_interval; > > @@ -146,7 +156,10 @@ static inline void ww_acquire_init(struct > > ww_acquire_ctx *ctx, > > debug_check_no_locks_freed((void *)ctx, sizeof(*ctx)); > > lockdep_init_map(&ctx->dep_map, ww_class->acquire_name, > > &ww_class->acquire_key, 0); > > + lockdep_init_map_wait(&ctx->first_lock_dep_map, ww_class- > > >mutex_name, > > + &ww_class->mutex_key, 0, > > LD_WAIT_SLEEP); > > mutex_acquire(&ctx->dep_map, 0, 0, _RET_IP_); > > + mutex_acquire_nest(&ctx->first_lock_dep_map, 0, 0, &ctx- > > >dep_map, _RET_IP_); > > #endif > > #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH > > ctx->deadlock_inject_interval = 1; > > @@ -185,6 +198,7 @@ static inline void ww_acquire_done(struct > > ww_acquire_ctx *ctx) > > static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx) > > { > > #ifdef CONFIG_DEBUG_LOCK_ALLOC > > + mutex_release(&ctx->first_lock_dep_map, _THIS_IP_); > > mutex_release(&ctx->dep_map, _THIS_IP_); > > #endif > > #ifdef DEBUG_WW_MUTEXES > > diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test- > > ww_mutex.c > > index 10a5736a21c2..5d58b2c0ef98 100644 > > --- a/kernel/locking/test-ww_mutex.c > > +++ b/kernel/locking/test-ww_mutex.c > > @@ -62,7 +62,8 @@ static int __test_mutex(unsigned int flags) > > int ret; > > > > ww_mutex_init(&mtx.mutex, &ww_class); > > - ww_acquire_init(&ctx, &ww_class); > > + if (flags & TEST_MTX_CTX) > > + ww_acquire_init(&ctx, &ww_class); > > > > INIT_WORK_ONSTACK(&mtx.work, test_mutex_work); > > init_completion(&mtx.ready); > > @@ -90,7 +91,8 @@ static int __test_mutex(unsigned int flags) > > ret = wait_for_completion_timeout(&mtx.done, > > TIMEOUT); > > } > > ww_mutex_unlock(&mtx.mutex); > > - ww_acquire_fini(&ctx); > > + if (flags & TEST_MTX_CTX) > > + ww_acquire_fini(&ctx); > > > > if (ret) { > > pr_err("%s(flags=%x): mutual exclusion failure\n", > > @@ -679,7 +681,7 @@ static int __init test_ww_mutex_init(void) > > if (ret) > > return ret; > > > > - ret = stress(2047, hweight32(STRESS_ALL)*ncpus, > > STRESS_ALL); > > + ret = stress(2046, hweight32(STRESS_ALL)*ncpus, > > STRESS_ALL); > > if (ret) > > return ret; > > > > diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c > > index 6f6a5fc85b42..6750321e3e9a 100644 > > --- a/lib/locking-selftest.c > > +++ b/lib/locking-selftest.c > > @@ -1720,8 +1720,6 @@ static void ww_test_normal(void) > > { > > int ret; > > > > - WWAI(&t); > > - > > /* > > * None of the ww_mutex codepaths should be taken in the > > 'normal' > > * mutex calls. The easiest way to verify this is by using > > the > > @@ -1770,6 +1768,8 @@ static void ww_test_normal(void) > > ww_mutex_base_unlock(&o.base); > > WARN_ON(o.ctx != (void *)~0UL); > > > > + WWAI(&t); > > + > > /* nest_lock */ > > o.ctx = (void *)~0UL; > > ww_mutex_base_lock_nest_lock(&o.base, &t); > > -- > > 2.46.0 > >
diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h index bb763085479a..45ff6f7a872b 100644 --- a/include/linux/ww_mutex.h +++ b/include/linux/ww_mutex.h @@ -65,6 +65,16 @@ struct ww_acquire_ctx { #endif #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; + /** + * @first_lock_dep_map: fake lockdep_map for first locked ww_mutex. + * + * lockdep requires the lockdep_map for the first locked ww_mutex + * in a ww transaction to remain in memory until all ww_mutexes of + * the transaction have been unlocked. Ensure this by keeping a + * fake locked ww_mutex lockdep map between ww_acquire_init() and + * ww_acquire_fini(). + */ + struct lockdep_map first_lock_dep_map; #endif #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH unsigned int deadlock_inject_interval; @@ -146,7 +156,10 @@ static inline void ww_acquire_init(struct ww_acquire_ctx *ctx, debug_check_no_locks_freed((void *)ctx, sizeof(*ctx)); lockdep_init_map(&ctx->dep_map, ww_class->acquire_name, &ww_class->acquire_key, 0); + lockdep_init_map_wait(&ctx->first_lock_dep_map, ww_class->mutex_name, + &ww_class->mutex_key, 0, LD_WAIT_SLEEP); mutex_acquire(&ctx->dep_map, 0, 0, _RET_IP_); + mutex_acquire_nest(&ctx->first_lock_dep_map, 0, 0, &ctx->dep_map, _RET_IP_); #endif #ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH ctx->deadlock_inject_interval = 1; @@ -185,6 +198,7 @@ static inline void ww_acquire_done(struct ww_acquire_ctx *ctx) static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx) { #ifdef CONFIG_DEBUG_LOCK_ALLOC + mutex_release(&ctx->first_lock_dep_map, _THIS_IP_); mutex_release(&ctx->dep_map, _THIS_IP_); #endif #ifdef DEBUG_WW_MUTEXES diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c index 10a5736a21c2..5d58b2c0ef98 100644 --- a/kernel/locking/test-ww_mutex.c +++ b/kernel/locking/test-ww_mutex.c @@ -62,7 +62,8 @@ static int __test_mutex(unsigned int flags) int ret; ww_mutex_init(&mtx.mutex, &ww_class); - ww_acquire_init(&ctx, &ww_class); + if (flags & TEST_MTX_CTX) + ww_acquire_init(&ctx, &ww_class); INIT_WORK_ONSTACK(&mtx.work, test_mutex_work); init_completion(&mtx.ready); @@ -90,7 +91,8 @@ static int __test_mutex(unsigned int flags) ret = wait_for_completion_timeout(&mtx.done, TIMEOUT); } ww_mutex_unlock(&mtx.mutex); - ww_acquire_fini(&ctx); + if (flags & TEST_MTX_CTX) + ww_acquire_fini(&ctx); if (ret) { pr_err("%s(flags=%x): mutual exclusion failure\n", @@ -679,7 +681,7 @@ static int __init test_ww_mutex_init(void) if (ret) return ret; - ret = stress(2047, hweight32(STRESS_ALL)*ncpus, STRESS_ALL); + ret = stress(2046, hweight32(STRESS_ALL)*ncpus, STRESS_ALL); if (ret) return ret; diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c index 6f6a5fc85b42..6750321e3e9a 100644 --- a/lib/locking-selftest.c +++ b/lib/locking-selftest.c @@ -1720,8 +1720,6 @@ static void ww_test_normal(void) { int ret; - WWAI(&t); - /* * None of the ww_mutex codepaths should be taken in the 'normal' * mutex calls. The easiest way to verify this is by using the @@ -1770,6 +1768,8 @@ static void ww_test_normal(void) ww_mutex_base_unlock(&o.base); WARN_ON(o.ctx != (void *)~0UL); + WWAI(&t); + /* nest_lock */ o.ctx = (void *)~0UL; ww_mutex_base_lock_nest_lock(&o.base, &t);