From d9b2c8714aef102dea95544a8cd9372b21af463f Mon Sep 17 00:00:00 2001 From: Artem Savkov Date: Mon, 9 Sep 2013 12:29:35 -0400 Subject: [PATCH] aio: rcu_read_lock protection for new rcu_dereference calls Patch "aio: fix rcu sparse warnings introduced by ioctx table lookup patch" (77d30b14d24e557f89c41980011d72428514d729 in linux-next.git) introduced a couple of new rcu_dereference calls which are not protected by rcu_read_lock and result in following warnings during syscall fuzzing(trinity): [ 471.646379] =============================== [ 471.649727] [ INFO: suspicious RCU usage. ] [ 471.653919] 3.11.0-next-20130906+ #496 Not tainted [ 471.657792] ------------------------------- [ 471.661235] fs/aio.c:503 suspicious rcu_dereference_check() usage! [ 471.665968] [ 471.665968] other info that might help us debug this: [ 471.665968] [ 471.672141] [ 471.672141] rcu_scheduler_active = 1, debug_locks = 1 [ 471.677549] 1 lock held by trinity-child0/3774: [ 471.681675] #0: (&(&mm->ioctx_lock)->rlock){+.+...}, at: [] SyS_io_setup+0x63a/0xc70 [ 471.688721] [ 471.688721] stack backtrace: [ 471.692488] CPU: 1 PID: 3774 Comm: trinity-child0 Not tainted 3.11.0-next-20130906+ #496 [ 471.698437] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 471.703151] 00000000 00000000 c58bbf30 c18a814b de2234c0 c58bbf58 c10a4ec6 c1b0d824 [ 471.709544] c1b0f60e 00000001 00000001 c1af61b0 00000000 cb670ac0 c3aca000 c58bbfac [ 471.716251] c119bc7c 00000002 00000001 00000000 c119b8dd 00000000 c10cf684 c58bbfb4 [ 471.722902] Call Trace: [ 471.724859] [] dump_stack+0x4b/0x66 [ 471.728772] [] lockdep_rcu_suspicious+0xc6/0x100 [ 471.733716] [] SyS_io_setup+0x89c/0xc70 [ 471.737806] [] ? SyS_io_setup+0x4fd/0xc70 [ 471.741689] [] ? __audit_syscall_entry+0x94/0xe0 [ 471.746080] [] syscall_call+0x7/0xb [ 471.749723] [] ? task_fork_fair+0x240/0x260 Signed-off-by: Artem Savkov Reviewed-by: Gu Zheng Signed-off-by: Benjamin LaHaise --- fs/aio.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/aio.c b/fs/aio.c index f4a27af6c9ac..6b868f0e0c4c 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -479,6 +479,7 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm) struct aio_ring *ring; spin_lock(&mm->ioctx_lock); + rcu_read_lock(); table = rcu_dereference(mm->ioctx_table); while (1) { @@ -487,6 +488,7 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm) if (!table->table[i]) { ctx->id = i; table->table[i] = ctx; + rcu_read_unlock(); spin_unlock(&mm->ioctx_lock); ring = kmap_atomic(ctx->ring_pages[0]); @@ -497,6 +499,7 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm) new_nr = (table ? table->nr : 1) * 4; + rcu_read_unlock(); spin_unlock(&mm->ioctx_lock); table = kzalloc(sizeof(*table) + sizeof(struct kioctx *) * @@ -507,6 +510,7 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm) table->nr = new_nr; spin_lock(&mm->ioctx_lock); + rcu_read_lock(); old = rcu_dereference(mm->ioctx_table); if (!old) { @@ -631,10 +635,12 @@ static void kill_ioctx(struct mm_struct *mm, struct kioctx *ctx) struct kioctx_table *table; spin_lock(&mm->ioctx_lock); + rcu_read_lock(); table = rcu_dereference(mm->ioctx_table); WARN_ON(ctx != table->table[ctx->id]); table->table[ctx->id] = NULL; + rcu_read_unlock(); spin_unlock(&mm->ioctx_lock); /* percpu_ref_kill() will do the necessary call_rcu() */ -- 2.39.2