2023-08-09 02:10:21

by Su Hui

Subject: [PATCH] fanotify: avoid possible NULL dereference

smatch error:
fs/notify/fanotify/fanotify_user.c:462 copy_fid_info_to_user():
we previously assumed 'fh' could be null (see line 421)

Fixes: afc894c784c8 ("fanotify: Store fanotify handles differently")
Signed-off-by: Su Hui <[email protected]>
---
fs/notify/fanotify/fanotify_user.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index f69c451018e3..5a5487ae2460 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -459,12 +459,13 @@ static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
if (WARN_ON_ONCE(len < sizeof(handle)))
return -EFAULT;

- handle.handle_type = fh->type;
handle.handle_bytes = fh_len;

/* Mangle handle_type for bad file_handle */
if (!fh_len)
handle.handle_type = FILEID_INVALID;
+ else
+ handle.handle_type = fh->type;

if (copy_to_user(buf, &handle, sizeof(handle)))
return -EFAULT;
--
2.30.2

2023-08-10 19:51:15

by Amir Goldstein

Subject: Re: [PATCH] fanotify: avoid possible NULL dereference

On Tue, Aug 8, 2023 at 12:19 PM Su Hui <[email protected]> wrote:
>
> smatch error:
> fs/notify/fanotify/fanotify_user.c:462 copy_fid_info_to_user():
> we previously assumed 'fh' could be null (see line 421)
>
> Fixes: afc894c784c8 ("fanotify: Store fanotify handles differently")
> Signed-off-by: Su Hui <[email protected]>'

Reviewed-by: Amir Goldstein <[email protected]>

> ---
> fs/notify/fanotify/fanotify_user.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index f69c451018e3..5a5487ae2460 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -459,12 +459,13 @@ static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
> if (WARN_ON_ONCE(len < sizeof(handle)))
> return -EFAULT;
>
> - handle.handle_type = fh->type;
> handle.handle_bytes = fh_len;
>
> /* Mangle handle_type for bad file_handle */
> if (!fh_len)
> handle.handle_type = FILEID_INVALID;
> + else
> + handle.handle_type = fh->type;
>
> if (copy_to_user(buf, &handle, sizeof(handle)))
> return -EFAULT;
> --
> 2.30.2
>

2024-01-02 13:48:08

by Jan Kara

Subject: Re: [PATCH] fanotify: avoid possible NULL dereference

On Thu 10-08-23 20:58:16, Amir Goldstein wrote:
> On Tue, Aug 8, 2023 at 12:19 PM Su Hui <[email protected]> wrote:
> >
> > smatch error:
> > fs/notify/fanotify/fanotify_user.c:462 copy_fid_info_to_user():
> > we previously assumed 'fh' could be null (see line 421)
> >
> > Fixes: afc894c784c8 ("fanotify: Store fanotify handles differently")
> > Signed-off-by: Su Hui <[email protected]>'
>
> Reviewed-by: Amir Goldstein <[email protected]>

I'm sorry but this has somehow fallen through the cracks.

> > diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> > index f69c451018e3..5a5487ae2460 100644
> > --- a/fs/notify/fanotify/fanotify_user.c
> > +++ b/fs/notify/fanotify/fanotify_user.c
> > @@ -459,12 +459,13 @@ static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
> > if (WARN_ON_ONCE(len < sizeof(handle)))
> > return -EFAULT;
> >
> > - handle.handle_type = fh->type;
> > handle.handle_bytes = fh_len;

Well, if passed 'fh' is NULL, we have problems later in the function
anyway. E.g. in fanotify_fh_buf() a few lines below. So I think this needs
a bit more work that just this small fixup...

Honza

> >
> > /* Mangle handle_type for bad file_handle */
> > if (!fh_len)
> > handle.handle_type = FILEID_INVALID;
> > + else
> > + handle.handle_type = fh->type;
> >
> > if (copy_to_user(buf, &handle, sizeof(handle)))
> > return -EFAULT;
> > --
> > 2.30.2
> >
--
Jan Kara <[email protected]>
SUSE Labs, CR