tty: fix when iov_iter_count() returns 0 in tty_write()
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Message ID 20210217144347.2962551-1-snovitoll@gmail.com
State New, archived
Headers show
Series
  • tty: fix when iov_iter_count() returns 0 in tty_write()
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Commit Message

Sabyrzhan Tasbolatov Feb. 17, 2021, 2:43 p.m. UTC
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: 494e63ee9c("tty: implement write_iter")
Reported-by: syzbot+3d2c27c2b7dc2a94814d@syzkaller.appspotmail.com
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
---
 drivers/tty/tty_io.c | 3 +++
 1 file changed, 3 insertions(+)

Comments

Greg Kroah-Hartman Feb. 17, 2021, 3:13 p.m. UTC | #1
On Wed, Feb 17, 2021 at 08:43:47PM +0600, 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: 494e63ee9c("tty: implement write_iter")

Nit, you need a ' ' before your '(' character here, otherwise the
linux-next scripts will complain.

> Reported-by: syzbot+3d2c27c2b7dc2a94814d@syzkaller.appspotmail.com
> Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
> ---
>  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..8d6d579ecc3b 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 -EINVAL;

According to the man page for write(2), I think this is the wrong error
value to return, unless that is the value that was returned on kernels
before the commit listed above.

Can you verify this?

thanks,

greg k-h
Greg Kroah-Hartman Feb. 17, 2021, 3:15 p.m. UTC | #2
On Wed, Feb 17, 2021 at 04:13:58PM +0100, Greg KH wrote:
> On Wed, Feb 17, 2021 at 08:43:47PM +0600, 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: 494e63ee9c("tty: implement write_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,

greg k-h

Patch
diff mbox series

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 816e709afa56..8d6d579ecc3b 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 -EINVAL;
+
 	ret = tty_write_lock(tty, file->f_flags & O_NDELAY);
 	if (ret < 0)
 		return ret;