Subject: + fanotify-check-file-flags-passed-in-fanotify_init.patch added to -mm tree
To: xypron.glpk@xxxxxx,Valdis.Kletnieks@xxxxxx,jack@xxxxxxx,mtk.manpages@xxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Wed, 14 May 2014 16:59:01 -0700
The patch titled
Subject: fanotify: check file flags passed in fanotify_init
has been added to the -mm tree. Its filename is
fanotify-check-file-flags-passed-in-fanotify_init.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/fanotify-check-file-flags-passed-in-fanotify_init.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/fanotify-check-file-flags-passed-in-fanotify_init.patch
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From: Heinrich Schuchardt <xypron.glpk@xxxxxx>
Subject: fanotify: check file flags passed in fanotify_init
Without this patch fanotify_init does not validate the value passed in
event_f_flags.
When a fanotify event is read from the fanotify file descriptor a new file
descriptor is created where file.f_flags = event_f_flags.
Internal and external open flags are stored together in field f_flags of
struct file. Hence, an application might create file descriptors with
internal flags like FMODE_EXEC, FMODE_NOCMTIME set.
Jan Kara and Eric Paris both aggreed that this is a bug and the value of
event_f_flags should be checked:
https://lkml.org/lkml/2014/4/29/522
https://lkml.org/lkml/2014/4/29/539
This updated patch version considers the comments by Michael Kerrisk in
https://lkml.org/lkml/2014/5/4/10
With the patch the value of event_f_flags is checked.
When specifying an invalid value error EINVAL is returned.
Internal flags are disallowed.
File creation flags are disallowed:
O_CREAT, O_DIRECTORY, O_EXCL, O_NOCTTY, O_NOFOLLOW, O_TRUNC, and O_TTY_INIT.
Flags which do not make sense with fanotify are disallowed:
__O_TMPFILE, O_PATH, FASYNC, and O_DIRECT.
This leaves us with the following allowed values:
O_RDONLY, O_WRONLY, O_RDWR are basic functionality. The are stored in the
bits given by O_ACCMODE.
O_APPEND is working as expected. The value might be useful in a logging
application which appends the current status each time the log is opened.
O_LARGEFILE is needed for files exceeding 4GB on 32bit systems.
O_NONBLOCK may be useful when monitoring slow devices like tapes.
O_NDELAY is equal to O_NONBLOCK except for platform parisc.
To avoid code breaking on parisc either both flags should be
allowed or none. The patch allows both.
__O_SYNC and O_DSYNC may be used to avoid data loss on power disruption.
O_NOATIME may be useful to reduce disk activity.
O_CLOEXEC may be useful, if separate processes shall be used to scan files.
Once this patch is accepted, the fanotify_init.2 manpage has to be updated.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@xxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Cc: Valdis Kletnieks <Valdis.Kletnieks@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/notify/fanotify/fanotify_user.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)
diff -puN fs/notify/fanotify/fanotify_user.c~fanotify-check-file-flags-passed-in-fanotify_init fs/notify/fanotify/fanotify_user.c
--- a/fs/notify/fanotify/fanotify_user.c~fanotify-check-file-flags-passed-in-fanotify_init
+++ a/fs/notify/fanotify/fanotify_user.c
@@ -25,6 +25,19 @@
#define FANOTIFY_DEFAULT_MAX_MARKS 8192
#define FANOTIFY_DEFAULT_MAX_LISTENERS 128
+/*
+ * All flags that may be specified in parameter event_f_flags of fanotify_init.
+ *
+ * Internal and external open flags are stored together in field f_flags of
+ * struct file. Only external open flags shall be allowed in event_f_flags.
+ * Internal flags like FMODE_NONOTIFY, FMODE_EXEC, FMODE_NOCMTIME shall be
+ * excluded.
+ */
+#define FANOTIFY_INIT_ALL_EVENT_F_BITS ( \
+ O_ACCMODE | O_APPEND | O_NONBLOCK | \
+ __O_SYNC | O_DSYNC | O_CLOEXEC | \
+ O_LARGEFILE | O_NOATIME )
+
extern const struct fsnotify_ops fanotify_fsnotify_ops;
static struct kmem_cache *fanotify_mark_cache __read_mostly;
@@ -669,6 +682,18 @@ SYSCALL_DEFINE2(fanotify_init, unsigned
if (flags & ~FAN_ALL_INIT_FLAGS)
return -EINVAL;
+ if (event_f_flags & ~FANOTIFY_INIT_ALL_EVENT_F_BITS)
+ return -EINVAL;
+
+ switch (event_f_flags & O_ACCMODE) {
+ case O_RDONLY:
+ case O_RDWR:
+ case O_WRONLY:
+ break;
+ default:
+ return -EINVAL;
+ }
+
user = get_current_user();
if (atomic_read(&user->fanotify_listeners) > FANOTIFY_DEFAULT_MAX_LISTENERS) {
free_uid(user);
_
Patches currently in -mm which might be from xypron.glpk@xxxxxx are
fanotify-fan_mark_flush-avoid-having-to-provide-a-fake-invalid-fd-and-path.patch
fanotify-create-fan_access-event-for-readdir.patch
fs-notify-fanotify-fanotify_userc-fix-fan_mark_flush-flag-checking.patch
fanotify-check-file-flags-passed-in-fanotify_init.patch
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