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authorTejun Heo <tj@kernel.org>2018-03-14 12:10:17 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-03-22 09:18:00 +0100
commitaa14f4bd6c4f32b19cdbfe37d918d1cb3baaf260 (patch)
treeee86697312c6ee17328944f92be7f273bb9be4b2 /fs
parent48226104275c0d8ddf307e432de8f6e6c5316bff (diff)
fs/aio: Use RCU accessors for kioctx_table->table[]
commit d0264c01e7587001a8c4608a5d1818dba9a4c11a upstream. While converting ioctx index from a list to a table, db446a08c23d ("aio: convert the ioctx list to table lookup v3") missed tagging kioctx_table->table[] as an array of RCU pointers and using the appropriate RCU accessors. This introduces a small window in the lookup path where init and access may race. Mark kioctx_table->table[] with __rcu and use the approriate RCU accessors when using the field. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Jann Horn <jannh@google.com> Fixes: db446a08c23d ("aio: convert the ioctx list to table lookup v3") Cc: Benjamin LaHaise <bcrl@kvack.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: stable@vger.kernel.org # v3.12+ Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/aio.c21
1 files changed, 11 insertions, 10 deletions
diff --git a/fs/aio.c b/fs/aio.c
index c00eb7e9cd04..0606f033cd9b 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -68,9 +68,9 @@ struct aio_ring {
#define AIO_RING_PAGES 8
struct kioctx_table {
- struct rcu_head rcu;
- unsigned nr;
- struct kioctx *table[];
+ struct rcu_head rcu;
+ unsigned nr;
+ struct kioctx __rcu *table[];
};
struct kioctx_cpu {
@@ -330,7 +330,7 @@ static int aio_ring_mremap(struct vm_area_struct *vma)
for (i = 0; i < table->nr; i++) {
struct kioctx *ctx;
- ctx = table->table[i];
+ ctx = rcu_dereference(table->table[i]);
if (ctx && ctx->aio_ring_file == file) {
if (!atomic_read(&ctx->dead)) {
ctx->user_id = ctx->mmap_base = vma->vm_start;
@@ -659,9 +659,9 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
while (1) {
if (table)
for (i = 0; i < table->nr; i++)
- if (!table->table[i]) {
+ if (!rcu_access_pointer(table->table[i])) {
ctx->id = i;
- table->table[i] = ctx;
+ rcu_assign_pointer(table->table[i], ctx);
spin_unlock(&mm->ioctx_lock);
/* While kioctx setup is in progress,
@@ -836,8 +836,8 @@ static int kill_ioctx(struct mm_struct *mm, struct kioctx *ctx,
}
table = rcu_dereference_raw(mm->ioctx_table);
- WARN_ON(ctx != table->table[ctx->id]);
- table->table[ctx->id] = NULL;
+ WARN_ON(ctx != rcu_access_pointer(table->table[ctx->id]));
+ RCU_INIT_POINTER(table->table[ctx->id], NULL);
spin_unlock(&mm->ioctx_lock);
/* free_ioctx_reqs() will do the necessary RCU synchronization */
@@ -882,7 +882,8 @@ void exit_aio(struct mm_struct *mm)
skipped = 0;
for (i = 0; i < table->nr; ++i) {
- struct kioctx *ctx = table->table[i];
+ struct kioctx *ctx =
+ rcu_dereference_protected(table->table[i], true);
if (!ctx) {
skipped++;
@@ -1071,7 +1072,7 @@ static struct kioctx *lookup_ioctx(unsigned long ctx_id)
if (!table || id >= table->nr)
goto out;
- ctx = table->table[id];
+ ctx = rcu_dereference(table->table[id]);
if (ctx && ctx->user_id == ctx_id) {
percpu_ref_get(&ctx->users);
ret = ctx;