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locking fixes

GIT PULL Ingo Molnar 1 participant 1 message Oct 18, 2016

Subsystems (3)
x86 VFS File locking (flock() and fcntl()/lockf())
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Ingo Molnar

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Linus,

Please pull the latest locking-urgent-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking-urgent-for-linus

# HEAD: 5f43086bb9224987010460dcf3dee68fbd4f574d locking, fs/locks: Add missing file_sem locks

Two fixes:

- a file locks fix (missing critical section, bug introduced in this merge window)
- an x86 down_write() stack frame annotation

Thanks,

Ingo

------------------>
Josh Poimboeuf (1):
locking/rwsem/x86: Add stack frame dependency for ____down_write()

Peter Zijlstra (1):
locking, fs/locks: Add missing file_sem locks

 arch/x86/include/asm/rwsem.h | 6 ++++--
 fs/locks.c                   | 6 ++++++
 2 files changed, 10 insertions(+), 2 deletions(-)
arch/x86/include/asm/rwsem.h +4 -2
index 3d33a719f5c1..a34e0d4b957d 100644
@@ -103,8 +103,10 @@ static inline bool __down_read_trylock(struct rw_semaphore *sem)
 ({							\
 	long tmp;					\
 	struct rw_semaphore* ret;			\
+	register void *__sp asm(_ASM_SP);		\
+							\
 	asm volatile("# beginning down_write\n\t"	\
-		     LOCK_PREFIX "  xadd      %1,(%3)\n\t"	\
+		     LOCK_PREFIX "  xadd      %1,(%4)\n\t"	\
 		     /* adds 0xffff0001, returns the old value */ \
 		     "  test " __ASM_SEL(%w1,%k1) "," __ASM_SEL(%w1,%k1) "\n\t" \
 		     /* was the active mask 0 before? */\

@@ -112,7 +114,7 @@ static inline bool __down_read_trylock(struct rw_semaphore *sem)
 		     "  call " slow_path "\n"		\
 		     "1:\n"				\
 		     "# ending down_write"		\
-		     : "+m" (sem->count), "=d" (tmp), "=a" (ret)	\
+		     : "+m" (sem->count), "=d" (tmp), "=a" (ret), "+r" (__sp) \
 		     : "a" (sem), "1" (RWSEM_ACTIVE_WRITE_BIAS) \
 		     : "memory", "cc");			\
 	ret;						\
fs/locks.c +6 -0
index ce93b416b490..22c5b4aa4961 100644
@@ -1609,6 +1609,7 @@ int fcntl_getlease(struct file *filp)
 
 	ctx = smp_load_acquire(&inode->i_flctx);
 	if (ctx && !list_empty_careful(&ctx->flc_lease)) {
+		percpu_down_read_preempt_disable(&file_rwsem);
 		spin_lock(&ctx->flc_lock);
 		time_out_leases(inode, &dispose);
 		list_for_each_entry(fl, &ctx->flc_lease, fl_list) {

@@ -1618,6 +1619,8 @@ int fcntl_getlease(struct file *filp)
 			break;
 		}
 		spin_unlock(&ctx->flc_lock);
+		percpu_up_read_preempt_enable(&file_rwsem);
+
 		locks_dispose_list(&dispose);
 	}
 	return type;

@@ -2529,11 +2532,14 @@ locks_remove_lease(struct file *filp, struct file_lock_context *ctx)
 	if (list_empty(&ctx->flc_lease))
 		return;
 
+	percpu_down_read_preempt_disable(&file_rwsem);
 	spin_lock(&ctx->flc_lock);
 	list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, fl_list)
 		if (filp == fl->fl_file)
 			lease_modify(fl, F_UNLCK, &dispose);
 	spin_unlock(&ctx->flc_lock);
+	percpu_up_read_preempt_enable(&file_rwsem);
+
 	locks_dispose_list(&dispose);
 }