The pre-content events require some extra thinking, especially around page faults. In order to make sure we don't advertise a feature working that doesn't actually work, add a flag to allow file systems to opt-in to this behavior.
Signed-off-by: Josef Bacik <[email protected]> --- fs/notify/fanotify/fanotify_user.c | 2 ++ include/linux/fs.h | 1 + include/linux/fsnotify.h | 4 ++++ 3 files changed, 7 insertions(+) diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index 53eee8af34a0..936e9f9e0cbc 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -1736,6 +1736,8 @@ static int fanotify_events_supported(struct fsnotify_group *group, /* Pre-content events are only supported on regular files and dirs */ if (mask & FANOTIFY_PRE_CONTENT_EVENTS) { + if (!(path->mnt->mnt_sb->s_type->fs_flags & FS_ALLOW_HSM)) + return -EINVAL; if (!is_dir && !d_is_reg(path->dentry)) return -EINVAL; if (is_dir && mask & FAN_PRE_MODIFY) diff --git a/include/linux/fs.h b/include/linux/fs.h index fd34b5755c0b..5708e91d3625 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2494,6 +2494,7 @@ struct file_system_type { #define FS_USERNS_MOUNT 8 /* Can be mounted by userns root */ #define FS_DISALLOW_NOTIFY_PERM 16 /* Disable fanotify permission events */ #define FS_ALLOW_IDMAP 32 /* FS has been updated to handle vfs idmappings. */ +#define FS_ALLOW_HSM 64 /* FS can handle fanotify pre-content events. */ #define FS_RENAME_DOES_D_MOVE 32768 /* FS will handle d_move() during rename() internally. */ int (*init_fs_context)(struct fs_context *); const struct fs_parameter_spec *parameters; diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h index 9d001d328619..27992b548f0c 100644 --- a/include/linux/fsnotify.h +++ b/include/linux/fsnotify.h @@ -179,6 +179,10 @@ static inline int fsnotify_file_area_perm(struct file *file, int perm_mask, if (!S_ISDIR(inode->i_mode) && !S_ISREG(inode->i_mode)) return 0; + /* The fs doesn't support pre-content events. */ + if (!(inode->i_sb->s_type->fs_flags & FS_ALLOW_HSM)) + return 0; + if (perm_mask & MAY_WRITE) fsnotify_mask = FS_PRE_MODIFY; else if (perm_mask & (MAY_READ | MAY_ACCESS)) -- 2.43.0
