Most pseudo files are not applicable for fsnotify events at all,
let alone to the new pre-content events.
Disable notifications to all files allocated with alloc_file_pseudo()
and enable legacy inotify events for the specific cases of pipe and
socket, which have known users of inotify events.
Pre-content events are also kept disabled for sockets and pipes.
Fixes: 20bf82a898b6 ("mm: don't allow huge faults for files with pre content watches")
Reported-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
Closes: https://lore.kernel.org/linux-fsdevel/20250131121703.1e4d00a7.alex.williamson@xxxxxxxxxx/
Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/linux-fsdevel/CAHk-=wi2pThSVY=zhO=ZKxViBj5QCRX-=AS2+rVknQgJnHXDFg@xxxxxxxxxxxxxx/
Tested-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/file_table.c | 11 +++++++++++
fs/open.c | 4 ++--
fs/pipe.c | 6 ++++++
net/socket.c | 5 +++++
4 files changed, 24 insertions(+), 2 deletions(-)
diff --git a/fs/file_table.c b/fs/file_table.c
index f0291a66f9db4..35b93da6c5cb1 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -375,7 +375,13 @@ struct file *alloc_file_pseudo(struct inode *inode, struct vfsmount *mnt,
if (IS_ERR(file)) {
ihold(inode);
path_put(&path);
+ return file;
}
+ /*
+ * Disable all fsnotify events for pseudo files by default.
+ * They may be enabled by caller with file_set_fsnotify_mode().
+ */
+ file_set_fsnotify_mode(file, FMODE_NONOTIFY);
return file;
}
EXPORT_SYMBOL(alloc_file_pseudo);
@@ -400,6 +406,11 @@ struct file *alloc_file_pseudo_noaccount(struct inode *inode,
return file;
}
file_init_path(file, &path, fops);
+ /*
+ * Disable all fsnotify events for pseudo files by default.
+ * They may be enabled by caller with file_set_fsnotify_mode().
+ */
+ file_set_fsnotify_mode(file, FMODE_NONOTIFY);
return file;
}
EXPORT_SYMBOL_GPL(alloc_file_pseudo_noaccount);
diff --git a/fs/open.c b/fs/open.c
index 3fcbfff8aede8..1be20de9f283a 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -936,8 +936,8 @@ static int do_dentry_open(struct file *f,
/*
* Set FMODE_NONOTIFY_* bits according to existing permission watches.
- * If FMODE_NONOTIFY was already set for an fanotify fd, this doesn't
- * change anything.
+ * If FMODE_NONOTIFY mode was already set for an fanotify fd or for a
+ * pseudo file, this call will not change the mode.
*/
file_set_fsnotify_mode_from_watchers(f);
error = fsnotify_open_perm(f);
diff --git a/fs/pipe.c b/fs/pipe.c
index 94b59045ab44b..ce1af7592780d 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -960,6 +960,12 @@ int create_pipe_files(struct file **res, int flags)
res[1] = f;
stream_open(inode, res[0]);
stream_open(inode, res[1]);
+ /*
+ * Disable permission and pre-content events, but enable legacy
+ * inotify events for legacy users.
+ */
+ file_set_fsnotify_mode(res[0], FMODE_NONOTIFY_PERM);
+ file_set_fsnotify_mode(res[1], FMODE_NONOTIFY_PERM);
return 0;
}
diff --git a/net/socket.c b/net/socket.c
index 262a28b59c7f0..28bae5a942341 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -479,6 +479,11 @@ struct file *sock_alloc_file(struct socket *sock, int flags, const char *dname)
sock->file = file;
file->private_data = sock;
stream_open(SOCK_INODE(sock), file);
+ /*
+ * Disable permission and pre-content events, but enable legacy
+ * inotify events for legacy users.
+ */
+ file_set_fsnotify_mode(file, FMODE_NONOTIFY_PERM);
return file;
}
EXPORT_SYMBOL(sock_alloc_file);
--
2.34.1
