9e67589a4a
[ Upstream commit 5d8f805789072ea7fd39504694b7bd17e5f751c4 ] We got the following issue in our fault injection stress test: ================================================================== BUG: KASAN: slab-use-after-free in cachefiles_withdraw_cookie+0x4d9/0x600 Read of size 8 at addr ffff888118efc000 by task kworker/u78:0/109 CPU: 13 PID: 109 Comm: kworker/u78:0 Not tainted 6.8.0-dirty #566 Call Trace: <TASK> kasan_report+0x93/0xc0 cachefiles_withdraw_cookie+0x4d9/0x600 fscache_cookie_state_machine+0x5c8/0x1230 fscache_cookie_worker+0x91/0x1c0 process_one_work+0x7fa/0x1800 [...] Allocated by task 117: kmalloc_trace+0x1b3/0x3c0 cachefiles_acquire_volume+0xf3/0x9c0 fscache_create_volume_work+0x97/0x150 process_one_work+0x7fa/0x1800 [...] Freed by task 120301: kfree+0xf1/0x2c0 cachefiles_withdraw_cache+0x3fa/0x920 cachefiles_put_unbind_pincount+0x1f6/0x250 cachefiles_daemon_release+0x13b/0x290 __fput+0x204/0xa00 task_work_run+0x139/0x230 do_exit+0x87a/0x29b0 [...] ================================================================== Following is the process that triggers the issue: p1 | p2 ------------------------------------------------------------ fscache_begin_lookup fscache_begin_volume_access fscache_cache_is_live(fscache_cache) cachefiles_daemon_release cachefiles_put_unbind_pincount cachefiles_daemon_unbind cachefiles_withdraw_cache fscache_withdraw_cache fscache_set_cache_state(cache, FSCACHE_CACHE_IS_WITHDRAWN); cachefiles_withdraw_objects(cache) fscache_wait_for_objects(fscache) atomic_read(&fscache_cache->object_count) == 0 fscache_perform_lookup cachefiles_lookup_cookie cachefiles_alloc_object refcount_set(&object->ref, 1); object->volume = volume fscache_count_object(vcookie->cache); atomic_inc(&fscache_cache->object_count) cachefiles_withdraw_volumes cachefiles_withdraw_volume fscache_withdraw_volume __cachefiles_free_volume kfree(cachefiles_volume) fscache_cookie_state_machine cachefiles_withdraw_cookie cache = object->volume->cache; // cachefiles_volume UAF !!! After setting FSCACHE_CACHE_IS_WITHDRAWN, wait for all the cookie lookups to complete first, and then wait for fscache_cache->object_count == 0 to avoid the cookie exiting after the volume has been freed and triggering the above issue. Therefore call fscache_withdraw_volume() before calling cachefiles_withdraw_objects(). This way, after setting FSCACHE_CACHE_IS_WITHDRAWN, only the following two cases will occur: 1) fscache_begin_lookup fails in fscache_begin_volume_access(). 2) fscache_withdraw_volume() will ensure that fscache_count_object() has been executed before calling fscache_wait_for_objects(). Fixes: fe2140e2f57f ("cachefiles: Implement volume support") Suggested-by: Hou Tao <houtao1@huawei.com> Signed-off-by: Baokun Li <libaokun1@huawei.com> Link: https://lore.kernel.org/r/20240628062930.2467993-4-libaokun@huaweicloud.com Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Baokun Li <libaokun1@huawei.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.