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| author | Artem Savkov <artem.savkov@gmail.com> | 2013-09-09 12:29:35 -0400 |
|---|---|---|
| committer | Benjamin LaHaise <bcrl@kvack.org> | 2013-09-09 12:29:35 -0400 |
| commit | d9b2c8714aef102dea95544a8cd9372b21af463f (patch) | |
| tree | 6e4c09e321cb6b77d60706f87506376a6908b3e8 /fs/aio.c | |
| parent | d6c355c7dabcd753a75bc77d150d36328a355267 (diff) | |
| download | lwn-d9b2c8714aef102dea95544a8cd9372b21af463f.tar.gz lwn-d9b2c8714aef102dea95544a8cd9372b21af463f.zip | |
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: [<c119ba1a>] 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] [<c18a814b>] dump_stack+0x4b/0x66
[ 471.728772] [<c10a4ec6>] lockdep_rcu_suspicious+0xc6/0x100
[ 471.733716] [<c119bc7c>] SyS_io_setup+0x89c/0xc70
[ 471.737806] [<c119b8dd>] ? SyS_io_setup+0x4fd/0xc70
[ 471.741689] [<c10cf684>] ? __audit_syscall_entry+0x94/0xe0
[ 471.746080] [<c18b1fcc>] syscall_call+0x7/0xb
[ 471.749723] [<c1080000>] ? task_fork_fair+0x240/0x260
Signed-off-by: Artem Savkov <artem.savkov@gmail.com>
Reviewed-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
Diffstat (limited to 'fs/aio.c')
| -rw-r--r-- | fs/aio.c | 6 |
1 files changed, 6 insertions, 0 deletions
@@ -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() */ |