Messages in this thread | | | Subject | Re: [PATCH v2] tty: fix when iov_iter_count() returns 0 in tty_write() | From | Jiri Slaby <> | Date | Fri, 19 Feb 2021 10:17:55 +0100 |
| |
On 17. 02. 21, 16:55, Sabyrzhan Tasbolatov wrote: > syzbot found WARNING in iov_iter_revert[1] when iov_iter_count() returns 0, > therefore INT_MAX is passed to iov_iter_revert() causing > MAX_RW_COUNT > warning. > > static inline ssize_t do_tty_write() > { > .. > size_t count = iov_iter_count(from); > .. > size_t size = count; > if (ret != size) > iov_iter_revert(from, size-ret); > > [1] WARNING: lib/iov_iter.c:1090 > Call Trace: > do_tty_write drivers/tty/tty_io.c:967 [inline] > file_tty_write.constprop.0+0x55f/0x8f0 drivers/tty/tty_io.c:1048 > call_write_iter include/linux/fs.h:1901 [inline] > new_sync_write+0x426/0x650 fs/read_write.c:518 > vfs_write+0x791/0xa30 fs/read_write.c:605 > ksys_write+0x12d/0x250 fs/read_write.c:658 > > Fixes: 9bb48c82aced ("tty: implement write_iter") > Reported-by: syzbot+3d2c27c2b7dc2a94814d@syzkaller.appspotmail.com > Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com> > --- > > v2: Fixed "Fixed" tag to proper commit and changed write return to -EFAULT > as this statement is valid, tested via strace: > > write(3, NULL, 0) = -1 EFAULT (Bad address) > > Updated to -EFAULT, should be a valid exit code as > copy_from_iter(.., .., from) returns -EFAULT as well if *from is invalid > address.
Exactly, EFAULT is for invalid memory accesses. But this should be IMO EINVAL as it's an invalid argument.
BTW what's the reason vfs calls ->write with zero count of iter?
>> Nit, you need a ' ' before your '(' character here, otherwise the >> linux-next scripts will complain. > >> Also, you got the git commit id wrong, so this needs to be fixed up >> anyway. You are pointing to a merge point, I doubt that's what you want >> to point to here, right? > > Thanks! > --- > drivers/tty/tty_io.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c > index 816e709afa56..e1460cad8b7d 100644 > --- a/drivers/tty/tty_io.c > +++ b/drivers/tty/tty_io.c > @@ -905,6 +905,9 @@ static inline ssize_t do_tty_write( > ssize_t ret, written = 0; > unsigned int chunk; > > + if (!count) > + return -EFAULT; > + > ret = tty_write_lock(tty, file->f_flags & O_NDELAY); > if (ret < 0) > return ret; >
-- js
| |