hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IB5UKT
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We got the following issue in a fuzz test of randomly issuing the restore command:
================================================================== BUG: KASAN: slab-use-after-free in cachefiles_ondemand_daemon_read+0xb41/0xb60 Read of size 8 at addr ffff888122e84088 by task ondemand-04-dae/963
CPU: 13 PID: 963 Comm: ondemand-04-dae Not tainted 6.8.0-dirty #564 Call Trace: kasan_report+0x93/0xc0 cachefiles_ondemand_daemon_read+0xb41/0xb60 vfs_read+0x169/0xb50 ksys_read+0xf5/0x1e0
Allocated by task 116: kmem_cache_alloc+0x140/0x3a0 cachefiles_lookup_cookie+0x140/0xcd0 fscache_cookie_state_machine+0x43c/0x1230 [...]
Freed by task 792: kmem_cache_free+0xfe/0x390 cachefiles_put_object+0x241/0x480 fscache_cookie_state_machine+0x5c8/0x1230 [...] ==================================================================
Following is the process that triggers the issue:
mount | daemon_thread1 | daemon_thread2 ------------------------------------------------------------ cachefiles_withdraw_cookie cachefiles_ondemand_clean_object(object) cachefiles_ondemand_send_req REQ_A = kzalloc(sizeof(*req) + data_len) wait_for_completion(&REQ_A->done)
cachefiles_daemon_read cachefiles_ondemand_daemon_read REQ_A = cachefiles_ondemand_select_req msg->object_id = req->object->ondemand->ondemand_id ------ restore ------ cachefiles_ondemand_restore xas_for_each(&xas, req, ULONG_MAX) xas_set_mark(&xas, CACHEFILES_REQ_NEW)
cachefiles_daemon_read cachefiles_ondemand_daemon_read REQ_A = cachefiles_ondemand_select_req copy_to_user(_buffer, msg, n) xa_erase(&cache->reqs, id) complete(&REQ_A->done) ------ close(fd) ------ cachefiles_ondemand_fd_release cachefiles_put_object cachefiles_put_object kmem_cache_free(cachefiles_object_jar, object) REQ_A->object->ondemand->ondemand_id // object UAF !!!
When we see the request within xa_lock, req->object must not have been released yet, so grab the reference count of object before xa_unlock to avoid the above issue.
Fixes: 0a7e54c1959c ("cachefiles: resend an open request if the read request's object is closed") Signed-off-by: Baokun Li libaokun1@huawei.com --- fs/cachefiles/ondemand.c | 10 ++++++---- include/trace/events/cachefiles.h | 6 +++++- 2 files changed, 11 insertions(+), 5 deletions(-)
diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c index c1f8be89afca..0eb2160add45 100644 --- a/fs/cachefiles/ondemand.c +++ b/fs/cachefiles/ondemand.c @@ -226,10 +226,8 @@ static int cachefiles_ondemand_get_fd(struct cachefiles_req *req) u32 object_id; int ret, fd;
- ret = object->fscache.cache->ops->grab_object(&object->fscache, - cachefiles_obj_get_ondemand_fd) ? 0 : -EAGAIN; - if (ret) - return ret; + object->fscache.cache->ops->grab_object(&object->fscache, + cachefiles_obj_get_ondemand_fd);
cache = container_of(object->fscache.cache, struct cachefiles_cache, cache); @@ -356,6 +354,8 @@ ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache, radix_tree_iter_tag_clear(&cache->reqs, &iter, CACHEFILES_REQ_NEW); cache->req_id_next = iter.index + 1; refcount_inc(&req->ref); + req->object->fscache.cache->ops->grab_object(&req->object->fscache, + cachefiles_obj_get_read_req); xa_unlock(&cache->reqs);
id = iter.index; @@ -379,6 +379,8 @@ ssize_t cachefiles_ondemand_daemon_read(struct cachefiles_cache *cache, }
out: + req->object->fscache.cache->ops->put_object(&req->object->fscache, + cachefiles_obj_put_read_req); /* Remove error request and CLOSE request has no reply */ if (ret || msg->opcode == CACHEFILES_OP_CLOSE) { xa_lock(&cache->reqs); diff --git a/include/trace/events/cachefiles.h b/include/trace/events/cachefiles.h index d09e369e9d1e..90d87f0cbe15 100644 --- a/include/trace/events/cachefiles.h +++ b/include/trace/events/cachefiles.h @@ -23,6 +23,8 @@ enum cachefiles_obj_ref_trace { cachefiles_obj_put_wait_timeo, cachefiles_obj_get_ondemand_fd, cachefiles_obj_put_ondemand_fd, + cachefiles_obj_get_read_req, + cachefiles_obj_put_read_req, cachefiles_obj_ref__nr_traces };
@@ -47,7 +49,9 @@ enum cachefiles_obj_ref_trace { EM(fscache_obj_put_queue, "PUT queue") \ EM(fscache_obj_put_work, "PUT work") \ EM(cachefiles_obj_put_wait_retry, "PUT wait_retry") \ - E_(cachefiles_obj_put_wait_timeo, "PUT wait_timeo") + EM(cachefiles_obj_put_wait_timeo, "PUT wait_timeo") \ + EM(cachefiles_obj_get_read_req, "GET read_req") \ + E_(cachefiles_obj_put_read_req, "PUT read_req")
/* * Export enum symbols via userspace.