From 6933599697c96c3213c95f5f1fc7cb6abfd08c54 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Thu, 5 Nov 2015 18:43:43 -0800 Subject: inotify: hide internal kernel bits from fdinfo There was a report that my patch: inotify: actually check for invalid bits in sys_inotify_add_watch() broke CRIU. The reason is that CRIU looks up raw flags in /proc/$pid/fdinfo/* to figure out how to rebuild inotify watches and then passes those flags directly back in to the inotify API. One of those flags (FS_EVENT_ON_CHILD) is set in mark->mask, but is not part of the inotify API. It is used inside the kernel to _implement_ inotify but it is not and has never been part of the API. My patch above ensured that we only allow bits which are part of the API (IN_ALL_EVENTS). This broke CRIU. FS_EVENT_ON_CHILD is really internal to the kernel. It is set _anyway_ on all inotify marks. So, CRIU was really just trying to set a bit that was already set. This patch hides that bit from fdinfo. CRIU will not see the bit, not try to set it, and should work as before. We should not have been exposing this bit in the first place, so this is a good patch independent of the CRIU problem. Signed-off-by: Dave Hansen Reported-by: Andrey Wagin Acked-by: Andrey Vagin Acked-by: Cyrill Gorcunov Acked-by: Eric Paris Cc: Pavel Emelyanov Cc: John McCutchan Cc: Robert Love Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/notify/fdinfo.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'fs/notify') diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c index 6b6f0d472ae8..fd98e5100cab 100644 --- a/fs/notify/fdinfo.c +++ b/fs/notify/fdinfo.c @@ -83,9 +83,16 @@ static void inotify_fdinfo(struct seq_file *m, struct fsnotify_mark *mark) inode_mark = container_of(mark, struct inotify_inode_mark, fsn_mark); inode = igrab(mark->inode); if (inode) { + /* + * IN_ALL_EVENTS represents all of the mask bits + * that we expose to userspace. There is at + * least one bit (FS_EVENT_ON_CHILD) which is + * used only internally to the kernel. + */ + u32 mask = mark->mask & IN_ALL_EVENTS; seq_printf(m, "inotify wd:%x ino:%lx sdev:%x mask:%x ignored_mask:%x ", inode_mark->wd, inode->i_ino, inode->i_sb->s_dev, - mark->mask, mark->ignored_mask); + mask, mark->ignored_mask); show_mark_fhandle(m, inode); seq_putc(m, '\n'); iput(inode); -- cgit v1.2.3-59-g8ed1b