fs: fs_parser: avoid NULL param->string to kstrtouint
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Message ID 20190719124329.23207-1-nh26223.lmm@gmail.com
State New
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Series
  • fs: fs_parser: avoid NULL param->string to kstrtouint
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Commit Message

Yin Fengwei July 19, 2019, 12:43 p.m. UTC
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+398343b7c1b1b989228d@syzkaller.appspotmail.com
Fixes: 71cbb7570a9a ("vfs: Move the subtype parameter into fuse")

Signed-off-by: Yin Fengwei <nh26223.lmm@gmail.com>
---
 fs/fs_parser.c | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Dmitry Vyukov July 19, 2019, 1:37 p.m. UTC | #1
On Fri, Jul 19, 2019 at 2:44 PM Yin Fengwei <nh26223.lmm@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+398343b7c1b1b989228d@syzkaller.appspotmail.com
> Fixes: 71cbb7570a9a ("vfs: Move the subtype parameter into fuse")
>
> Signed-off-by: Yin Fengwei <nh26223.lmm@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
>
> --
> You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@googlegroups.com.
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Greg Kroah-Hartman July 19, 2019, 5:38 p.m. UTC | #2
On Fri, Jul 19, 2019 at 08:43:29PM +0800, Yin Fengwei 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+398343b7c1b1b989228d@syzkaller.appspotmail.com
> Fixes: 71cbb7570a9a ("vfs: Move the subtype parameter into fuse")
> 
> Signed-off-by: Yin Fengwei <nh26223.lmm@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;
> +			}

Always run checkpatch.pl so grumpy maintainers do not tell you to go run
checkpatch.pl :)
Yin Fengwei July 19, 2019, 11:28 p.m. UTC | #3
On Fri, Jul 19, 2019 at 03:37:37PM +0200, Dmitry Vyukov wrote:
> On Fri, Jul 19, 2019 at 2:44 PM Yin Fengwei <nh26223.lmm@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+398343b7c1b1b989228d@syzkaller.appspotmail.com
> > Fixes: 71cbb7570a9a ("vfs: Move the subtype parameter into fuse")
> >
> > Signed-off-by: Yin Fengwei <nh26223.lmm@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 ?
Yes. Should have ! in condition for NULL param->string. Will fix in v2.

Regards
Yin, Fengwei

> 
> > +                               goto bad_value;
> > +                       }
> > +
> >                         ret = kstrtouint(param->string, 0, &result->uint_32);
> >                         break;
> >                 case fs_value_is_file:
> > --
> > 2.17.1
> >
> > --
> > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group.
> > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@googlegroups.com.
> > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/20190719124329.23207-1-nh26223.lmm%40gmail.com.
Yin Fengwei July 19, 2019, 11:29 p.m. UTC | #4
On Fri, Jul 19, 2019 at 07:38:11PM +0200, Greg KH wrote:
> On Fri, Jul 19, 2019 at 08:43:29PM +0800, Yin Fengwei 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+398343b7c1b1b989228d@syzkaller.appspotmail.com
> > Fixes: 71cbb7570a9a ("vfs: Move the subtype parameter into fuse")
> > 
> > Signed-off-by: Yin Fengwei <nh26223.lmm@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;
> > +			}
> 
> Always run checkpatch.pl so grumpy maintainers do not tell you to go run
> checkpatch.pl :)

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

Regards
Yin, Fengwei

Patch
diff mbox series

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: