[PATCH] fs: fs_parser: avoid NULL param->string to kstrtouint

[Yin Fengwei]

syzbot reported general protection fault in kstrtouint:
https://lkml.org/lkml/2019/7/18/328

From the log, if the mount option is something like:
fd,XXXXXXXXXXXXXXXXXXXX

The default parameter (which has NULL param->string) will be
passed to vfs_parse_fs_param. Finally, this NULL param->string
is passed to kstrtouint and trigger NULL pointer access.

Reported-by: syzbot+398343...@syzkaller.appspotmail.com
Fixes: 71cbb7570a9a ("vfs: Move the subtype parameter into fuse")

Signed-off-by: Yin Fengwei <nh262...@gmail.com>
---
fs/fs_parser.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/fs/fs_parser.c b/fs/fs_parser.c
index d13fe7d797c2..578e6880ac67 100644
--- a/fs/fs_parser.c
+++ b/fs/fs_parser.c
@@ -210,6 +210,10 @@ int fs_parse(struct fs_context *fc,
case fs_param_is_fd: {
switch (param->type) {
case fs_value_is_string:
+ if (result->has_value) {
+ goto bad_value;
+ }
+
ret = kstrtouint(param->string, 0, &result->uint_32);
break;
case fs_value_is_file:
--
2.17.1

[Dmitry Vyukov]

On Fri, Jul 19, 2019 at 2:44 PM Yin Fengwei <nh262...@gmail.com> wrote:
>
> syzbot reported general protection fault in kstrtouint:
> https://lkml.org/lkml/2019/7/18/328
>
> From the log, if the mount option is something like:
> fd,XXXXXXXXXXXXXXXXXXXX
>
> The default parameter (which has NULL param->string) will be
> passed to vfs_parse_fs_param. Finally, this NULL param->string
> is passed to kstrtouint and trigger NULL pointer access.
>
> Reported-by: syzbot+398343...@syzkaller.appspotmail.com
> Fixes: 71cbb7570a9a ("vfs: Move the subtype parameter into fuse")
>
> Signed-off-by: Yin Fengwei <nh262...@gmail.com>
> ---
> fs/fs_parser.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/fs/fs_parser.c b/fs/fs_parser.c
> index d13fe7d797c2..578e6880ac67 100644
> --- a/fs/fs_parser.c
> +++ b/fs/fs_parser.c
> @@ -210,6 +210,10 @@ int fs_parse(struct fs_context *fc,
> case fs_param_is_fd: {
> switch (param->type) {
> case fs_value_is_string:
> + if (result->has_value) {

!result->has_value ?

> + goto bad_value;
> + }
> +
> ret = kstrtouint(param->string, 0, &result->uint_32);
> break;
> case fs_value_is_file:
> --
> 2.17.1
>

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[Greg KH]

Always run checkpatch.pl so grumpy maintainers do not tell you to go run
checkpatch.pl :)

[YinFengwei]

Yes. Should have ! in condition for NULL param->string. Will fix in v2.

Regards
Yin, Fengwei

[YinFengwei]

Thanks a lot for kindly reminder. Will be careful for future patch. :)

Regards
Yin, Fengwei

[Yin Fengwei]

syzbot reported general protection fault in kstrtouint:
https://lkml.org/lkml/2019/7/18/328

From the log, if the mount option is something like:
fd,XXXXXXXXXXXXXXXXXXXX

The default parameter (which has NULL param->string) will be
passed to vfs_parse_fs_param. Finally, this NULL param->string
is passed to kstrtouint and trigger NULL pointer access.

Reported-by: syzbot+398343...@syzkaller.appspotmail.com
Fixes: 71cbb7570a9a ("vfs: Move the subtype parameter into fuse")

Signed-off-by: Yin Fengwei <nh262...@gmail.com>
---

ChangeLog:
v1 -> v2:
- Fix typo in v1
- Remove braces {} from single statement blocks

fs/fs_parser.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/fs/fs_parser.c b/fs/fs_parser.c
index 83b66c9e9a24..7498a44f18c0 100644
--- a/fs/fs_parser.c
+++ b/fs/fs_parser.c
@@ -206,6 +206,9 @@ int fs_parse(struct fs_context *fc,

case fs_param_is_fd: {
switch (param->type) {
case fs_value_is_string:

+ if (!result->has_value)
+ goto bad_value;
+

[Eric Biggers]

Reviewed-by: Eric Biggers <ebig...@kernel.org>

Al, can you please apply this patch?

- Eric

[Eric Biggers]

[trimmed Cc list a bit]

Ping. Al, when are you going to apply this?

- Eric

[Al Viro]

On Wed, Aug 21, 2019 at 09:22:49PM -0700, Eric Biggers wrote:
> > > diff --git a/fs/fs_parser.c b/fs/fs_parser.c
> > > index 83b66c9e9a24..7498a44f18c0 100644
> > > --- a/fs/fs_parser.c
> > > +++ b/fs/fs_parser.c
> > > @@ -206,6 +206,9 @@ int fs_parse(struct fs_context *fc,
> > > case fs_param_is_fd: {
> > > switch (param->type) {
> > > case fs_value_is_string:
> > > + if (!result->has_value)
> > > + goto bad_value;
> > > +
> > > ret = kstrtouint(param->string, 0, &result->uint_32);
> > > break;
> > > case fs_value_is_file:
> > > --
> > > 2.17.1
> >
> > Reviewed-by: Eric Biggers <ebig...@kernel.org>
> >
> > Al, can you please apply this patch?
> >
> > - Eric
>
> Ping. Al, when are you going to apply this?

Sits in the local queue. Sorry, got seriously sidetracked into
configfs mess lately, will update for-next tomorrow and push
it out.