Commit 53b8fd79 authored by Baokun Li's avatar Baokun Li Committed by Zizhi Wo
Browse files

cachefiles: flush all requests after setting CACHEFILES_DEAD 

mainline inclusion
from mainline-v6.10-rc4
commit 85e833cd7243bda7285492b0653c3abb1e2e757b
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/IA6I1T

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=85e833cd7243bda7285492b0653c3abb1e2e757b



--------------------------------

In ondemand mode, when the daemon is processing an open request, if the
kernel flags the cache as CACHEFILES_DEAD, the cachefiles_daemon_write()
will always return -EIO, so the daemon can't pass the copen to the kernel.
Then the kernel process that is waiting for the copen triggers a hung_task.

Since the DEAD state is irreversible, it can only be exited by closing
/dev/cachefiles. Therefore, after calling cachefiles_io_error() to mark
the cache as CACHEFILES_DEAD, if in ondemand mode, flush all requests to
avoid the above hungtask. We may still be able to read some of the cached
data before closing the fd of /dev/cachefiles.

Note that this relies on the patch that adds reference counting to the req,
otherwise it may UAF.

Fixes: c8383054 ("cachefiles: notify the user daemon when looking up cookie")
Signed-off-by: default avatarBaokun Li <libaokun1@huawei.com>
Link: https://lore.kernel.org/r/20240522114308.2402121-12-libaokun@huaweicloud.com


Acked-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
Signed-off-by: default avatarZizhi Wo <wozizhi@huawei.com>
parent ca97d6ae

fs/cachefiles/daemon.c

+1 −1
Original line number Diff line number Diff line
@@ -133,7 +133,7 @@ static int cachefiles_daemon_open(struct inode *inode, struct file *file) 
	return 0;

}



static void cachefiles_flush_reqs(struct cachefiles_cache *cache)

void cachefiles_flush_reqs(struct cachefiles_cache *cache)

{

	struct xarray *xa = &cache->reqs;

	struct cachefiles_req *req;

fs/cachefiles/internal.h

+3 −0
Original line number Diff line number Diff line
@@ -188,6 +188,7 @@ extern int cachefiles_has_space(struct cachefiles_cache *cache, 
 * daemon.c

 */

extern const struct file_operations cachefiles_daemon_fops;

extern void cachefiles_flush_reqs(struct cachefiles_cache *cache);

extern void cachefiles_get_unbind_pincount(struct cachefiles_cache *cache);

extern void cachefiles_put_unbind_pincount(struct cachefiles_cache *cache);
@@ -426,6 +427,8 @@ do { \ 
	pr_err("I/O Error: " FMT"\n", ##__VA_ARGS__);	\

	fscache_io_error((___cache)->cache);		\

	set_bit(CACHEFILES_DEAD, &(___cache)->flags);	\

	if (cachefiles_in_ondemand_mode(___cache))	\

		cachefiles_flush_reqs(___cache);	\

} while (0)



#define cachefiles_io_error_obj(object, FMT, ...)			\