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author | Carlos Maiolino <cem@kernel.org> | 2024-03-20 13:39:59 +0100 |
---|---|---|
committer | Andrew Morton <akpm@linux-foundation.org> | 2024-03-26 11:07:23 -0700 |
commit | 0a69b6b3a026543bc215ccc866d0aea5579e6ce2 (patch) | |
tree | 261159c40ad9a7b4ff98dc0041c06c9204013cd3 | |
parent | 105840ebd76d8dbc1a7d734748ae320076f3201e (diff) | |
download | linux-stable-0a69b6b3a026543bc215ccc866d0aea5579e6ce2.tar.gz linux-stable-0a69b6b3a026543bc215ccc866d0aea5579e6ce2.tar.bz2 linux-stable-0a69b6b3a026543bc215ccc866d0aea5579e6ce2.zip |
tmpfs: fix race on handling dquot rbtree
A syzkaller reproducer found a race while attempting to remove dquot
information from the rb tree.
Fetching the rb_tree root node must also be protected by the
dqopt->dqio_sem, otherwise, giving the right timing, shmem_release_dquot()
will trigger a warning because it couldn't find a node in the tree, when
the real reason was the root node changing before the search starts:
Thread 1 Thread 2
- shmem_release_dquot() - shmem_{acquire,release}_dquot()
- fetch ROOT - Fetch ROOT
- acquire dqio_sem
- wait dqio_sem
- do something, triger a tree rebalance
- release dqio_sem
- acquire dqio_sem
- start searching for the node, but
from the wrong location, missing
the node, and triggering a warning.
Link: https://lkml.kernel.org/r/20240320124011.398847-1-cem@kernel.org
Fixes: eafc474e2029 ("shmem: prepare shmem quota infrastructure")
Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Reported-by: Ubisectech Sirius <bugreport@ubisectech.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
-rw-r--r-- | mm/shmem_quota.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/mm/shmem_quota.c b/mm/shmem_quota.c index 062d1c1097ae..ce514e700d2f 100644 --- a/mm/shmem_quota.c +++ b/mm/shmem_quota.c @@ -116,7 +116,7 @@ static int shmem_free_file_info(struct super_block *sb, int type) static int shmem_get_next_id(struct super_block *sb, struct kqid *qid) { struct mem_dqinfo *info = sb_dqinfo(sb, qid->type); - struct rb_node *node = ((struct rb_root *)info->dqi_priv)->rb_node; + struct rb_node *node; qid_t id = from_kqid(&init_user_ns, *qid); struct quota_info *dqopt = sb_dqopt(sb); struct quota_id *entry = NULL; @@ -126,6 +126,7 @@ static int shmem_get_next_id(struct super_block *sb, struct kqid *qid) return -ESRCH; down_read(&dqopt->dqio_sem); + node = ((struct rb_root *)info->dqi_priv)->rb_node; while (node) { entry = rb_entry(node, struct quota_id, node); @@ -165,7 +166,7 @@ out_unlock: static int shmem_acquire_dquot(struct dquot *dquot) { struct mem_dqinfo *info = sb_dqinfo(dquot->dq_sb, dquot->dq_id.type); - struct rb_node **n = &((struct rb_root *)info->dqi_priv)->rb_node; + struct rb_node **n; struct shmem_sb_info *sbinfo = dquot->dq_sb->s_fs_info; struct rb_node *parent = NULL, *new_node = NULL; struct quota_id *new_entry, *entry; @@ -176,6 +177,8 @@ static int shmem_acquire_dquot(struct dquot *dquot) mutex_lock(&dquot->dq_lock); down_write(&dqopt->dqio_sem); + n = &((struct rb_root *)info->dqi_priv)->rb_node; + while (*n) { parent = *n; entry = rb_entry(parent, struct quota_id, node); @@ -264,7 +267,7 @@ static bool shmem_is_empty_dquot(struct dquot *dquot) static int shmem_release_dquot(struct dquot *dquot) { struct mem_dqinfo *info = sb_dqinfo(dquot->dq_sb, dquot->dq_id.type); - struct rb_node *node = ((struct rb_root *)info->dqi_priv)->rb_node; + struct rb_node *node; qid_t id = from_kqid(&init_user_ns, dquot->dq_id); struct quota_info *dqopt = sb_dqopt(dquot->dq_sb); struct quota_id *entry = NULL; @@ -275,6 +278,7 @@ static int shmem_release_dquot(struct dquot *dquot) goto out_dqlock; down_write(&dqopt->dqio_sem); + node = ((struct rb_root *)info->dqi_priv)->rb_node; while (node) { entry = rb_entry(node, struct quota_id, node); |