When implementing connector fsid cache, we only initialized the cache
when the first mark added to object was added by FAN_REPORT_FID group.
We forgot to update conn->fsid when the second mark is added by
FAN_REPORT_FID group to an already attached connector without fsid
cache.
Reported-and-tested-by: syzbot+c277e8e2f46414645508@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 77115225acc6 ("fanotify: cache fsid in fsnotify_mark_connector")
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
Jan,
This fix has been confirmed by syzbot to fix the issue as well as
by my modification to Matthew's LTP test:
https://github.com/amir73il/ltp/commits/fanotify_dirent
Thanks,
Amir.
fs/notify/fanotify/fanotify.c | 4 ++++
fs/notify/mark.c | 14 +++++++++++---
include/linux/fsnotify_backend.h | 2 ++
3 files changed, 17 insertions(+), 3 deletions(-)
diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index e6fde1a5c072..b428c295d13f 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -355,6 +355,10 @@ static __kernel_fsid_t fanotify_get_fsid(struct fsnotify_iter_info *iter_info)
/* Mark is just getting destroyed or created? */
if (!conn)
continue;
+ if (!(conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID))
+ continue;
+ /* Pairs with smp_wmb() in fsnotify_add_mark_list() */
+ smp_rmb();
fsid = conn->fsid;
if (WARN_ON_ONCE(!fsid.val[0] && !fsid.val[1]))
continue;
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 25eb247ea85a..99ddd126f6f0 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -482,10 +482,13 @@ static int fsnotify_attach_connector_to_object(fsnotify_connp_t *connp,
conn->type = type;
conn->obj = connp;
/* Cache fsid of filesystem containing the object */
- if (fsid)
+ if (fsid) {
conn->fsid = *fsid;
- else
+ conn->flags = FSNOTIFY_CONN_FLAG_HAS_FSID;
+ } else {
conn->fsid.val[0] = conn->fsid.val[1] = 0;
+ conn->flags = 0;
+ }
if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
inode = igrab(fsnotify_conn_inode(conn));
/*
@@ -560,7 +563,12 @@ static int fsnotify_add_mark_list(struct fsnotify_mark *mark,
if (err)
return err;
goto restart;
- } else if (fsid && (conn->fsid.val[0] || conn->fsid.val[1]) &&
+ } else if (fsid && !(conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID)) {
+ conn->fsid = *fsid;
+ /* Pairs with smp_rmb() in fanotify_get_fsid() */
+ smp_wmb();
+ conn->flags |= FSNOTIFY_CONN_FLAG_HAS_FSID;
+ } else if (fsid && (conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID) &&
(fsid->val[0] != conn->fsid.val[0] ||
fsid->val[1] != conn->fsid.val[1])) {
/*
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index a9f9dcc1e515..da181dc05261 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -293,6 +293,8 @@ typedef struct fsnotify_mark_connector __rcu *fsnotify_connp_t;
struct fsnotify_mark_connector {
spinlock_t lock;
unsigned int type; /* Type of object [lock] */
+#define FSNOTIFY_CONN_FLAG_HAS_FSID 0x01
+ unsigned int flags; /* flags [lock] */
__kernel_fsid_t fsid; /* fsid of filesystem containing object */
union {
/* Object pointer [lock] */
--
2.17.1
