On Tue 12-03-19 14:59:27, Amir Goldstein wrote: > On Tue, Mar 12, 2019 at 1:45 PM Jan Kara <jack@xxxxxxx> wrote: > > > > Thanks for forwarding Andrew! > > > > On Mon 11-03-19 16:30:04, Andrew Morton wrote: > > > fyi > > > > > > Begin forwarded message: > > > > > > Date: Mon, 11 Mar 2019 13:42:06 -0700 > > > From: syzbot <syzbot+2c49971e251e36216d1f@xxxxxxxxxxxxxxxxxxxxxxxxx> > > > To: akpm@xxxxxxxxxxxxxxxxxxxx, cai@xxxxxx, crecklin@xxxxxxxxxx, keescook@xxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx, syzkaller-bugs@xxxxxxxxxxxxxxxx > > > Subject: WARNING: bad usercopy in fanotify_read > > > > > > > > > Hello, > > > > > > syzbot found the following crash on: > > > > > > HEAD commit: 12ad143e Merge branch 'perf-urgent-for-linus' of git://git.. > > > git tree: upstream > > > console output: https://syzkaller.appspot.com/x/log.txt?x=12776f57200000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=e9d91b7192a5e96e > > > dashboard link: https://syzkaller.appspot.com/bug?extid=2c49971e251e36216d1f > > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > > userspace arch: amd64 > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1287516f200000 > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17ee410b200000 > > > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > > Reported-by: syzbot+2c49971e251e36216d1f@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > > > ------------[ cut here ]------------ > > > 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 > > > > Yeah, right. We need to create fanotify_event cache so that copying of > > fanotify_event.fid.fh to userspace is allowed. Sadly the area is unioned > > with a possible slab pointer so that won't be protected from leaking but > > life is not perfect. Amir, something like attached patch? > > I agree. We could do something like this, to first copy the inline fh > from slab to short stack buf: > > static inline void *fanotify_fid_fh_user(struct fanotify_fid *fid, > unsigned int fh_len, char *fh_buf) > { > if (fh_len > FANOTIFY_INLINE_FH_LEN) > return fid->ext_fh; > memcpy(fh_buf, fid->fh, fh_len); > return fh_buf; > } > > But I don't think we should bother. OK, pushed my fix to my tree. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
