[PATCH 2/7] fs/aio: Use RCU accessors for kioctx_table->table[]
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
Reported-by: Jann Horn
Fixes: db446a08c23d ("aio: convert the ioctx list to table lookup v3")
Cc: Benjamin LaHaise
Cc: Linus Torvalds
Cc: sta...@vger.kernel.org
---
fs/aio.c | 21 +++--
1 file changed, 11 insertions(+), 10 deletions(-)
diff --git a/fs/aio.c b/fs/aio.c
index eb2e0cf..6bcd3fb 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;
- unsignednr;
- struct kioctx *table[];
+ struct rcu_head rcu;
+ unsignednr;
+ 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(>dead)) {
ctx->user_id = ctx->mmap_base = vma->vm_start;
@@ -666,9 +666,9 @@ 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(>ioctx_lock);
/* While kioctx setup is in progress,
@@ -849,8 +849,8 @@ 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(>ioctx_lock);
/* free_ioctx_reqs() will do the necessary RCU synchronization */
@@ -895,7 +895,8 @@ 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++;
@@ -1084,7 +1085,7 @@ 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(>users);
ret = ctx;
--
2.9.5
[PATCH 2/7] fs/aio: Use RCU accessors for kioctx_table->table[]
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
Reported-by: Jann Horn
Fixes: db446a08c23d ("aio: convert the ioctx list to table lookup v3")
Cc: Benjamin LaHaise
Cc: Linus Torvalds
Cc: sta...@vger.kernel.org
---
fs/aio.c | 21 +++--
1 file changed, 11 insertions(+), 10 deletions(-)
diff --git a/fs/aio.c b/fs/aio.c
index eb2e0cf..6bcd3fb 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;
- unsignednr;
- struct kioctx *table[];
+ struct rcu_head rcu;
+ unsignednr;
+ 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(>dead)) {
ctx->user_id = ctx->mmap_base = vma->vm_start;
@@ -666,9 +666,9 @@ 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(>ioctx_lock);
/* While kioctx setup is in progress,
@@ -849,8 +849,8 @@ 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(>ioctx_lock);
/* free_ioctx_reqs() will do the necessary RCU synchronization */
@@ -895,7 +895,8 @@ 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++;
@@ -1084,7 +1085,7 @@ 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(>users);
ret = ctx;
--
2.9.5
