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authorJan Kara <jack@suse.cz>2019-03-12 12:42:37 +0100
committerJan Kara <jack@suse.cz>2019-03-19 09:29:07 +0100
commitb2d22b6bb33aac10c415e4ba13c8eade201c6f09 (patch)
tree1610454690dd14fe250d0b6e8b6be1f580f1f360 /fs/notify
parent62c9d2674b31d4c8a674bee86b7edc6da2803aea (diff)
downloadlinux-stericsson-b2d22b6bb33aac10c415e4ba13c8eade201c6f09.tar.gz
fanotify: Allow copying of file handle to userspace
When file handle is embedded inside fanotify_event and usercopy checks are enabled, we get a warning like: Bad or missing usercopy whitelist? Kernel memory exposure attempt detected from SLAB object 'fanotify_event' (offset 40, size 8)! WARNING: CPU: 1 PID: 7649 at mm/usercopy.c:78 usercopy_warn+0xeb/0x110 mm/usercopy.c:78 Annotate handling in fanotify_event properly to mark copying it to userspace is fine. Reported-by: syzbot+2c49971e251e36216d1f@syzkaller.appspotmail.com Fixes: a8b13aa20afb ("fanotify: enable FAN_REPORT_FID init flag") Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs/notify')
-rw-r--r--fs/notify/fanotify/fanotify_user.c12
1 files changed, 11 insertions, 1 deletions
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 56992b32c6bb..a90bb19dcfa2 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -208,6 +208,7 @@ static int copy_fid_to_user(struct fanotify_event *event, char __user *buf)
{
struct fanotify_event_info_fid info = { };
struct file_handle handle = { };
+ unsigned char bounce[FANOTIFY_INLINE_FH_LEN], *fh;
size_t fh_len = event->fh_len;
size_t len = fanotify_event_info_len(event);
@@ -233,7 +234,16 @@ static int copy_fid_to_user(struct fanotify_event *event, char __user *buf)
buf += sizeof(handle);
len -= sizeof(handle);
- if (copy_to_user(buf, fanotify_event_fh(event), fh_len))
+ /*
+ * For an inline fh, copy through stack to exclude the copy from
+ * usercopy hardening protections.
+ */
+ fh = fanotify_event_fh(event);
+ if (fh_len <= FANOTIFY_INLINE_FH_LEN) {
+ memcpy(bounce, fh, fh_len);
+ fh = bounce;
+ }
+ if (copy_to_user(buf, fh, fh_len))
return -EFAULT;
/* Pad with 0's */