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cachefiles: flush all requests after setting CACHEFILES_DEAD

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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: c838305450 ("cachefiles: notify the user daemon when looking up cookie")
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Link: https://lore.kernel.org/r/20240522114308.2402121-12-libaokun@huaweicloud.com
Acked-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Baokun Li 2024-05-22 19:43:07 +08:00 committed by Christian Brauner
parent 4f8703fb34
commit 85e833cd72
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GPG Key ID: 91C61BC06578DCA2
2 changed files with 4 additions and 1 deletions
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2
fs/cachefiles/daemon.c
View File

@ -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;

3
fs/cachefiles/internal.h
View File

@ -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, ...) \