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| author | Jan Kara <jack@suse.cz> | 2019-03-12 14:42:37 +0300 |
|---|---|---|
| committer | Jan Kara <jack@suse.cz> | 2019-03-19 11:29:07 +0300 |
| commit | b2d22b6bb33aac10c415e4ba13c8eade201c6f09 (patch) | |
| tree | 1610454690dd14fe250d0b6e8b6be1f580f1f360 /fs | |
| parent | 62c9d2674b31d4c8a674bee86b7edc6da2803aea (diff) | |
| download | linux-b2d22b6bb33aac10c415e4ba13c8eade201c6f09.tar.xz | |
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')
| -rw-r--r-- | fs/notify/fanotify/fanotify_user.c | 12 |
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 */ |