diff mbox series

[-next] hugetlbfs: fix null-ptr-deref in hugetlbfs_parse_param()

Message ID 20221020231609.4810-1-yin31149@gmail.com
State New
Headers
Series [-next] hugetlbfs: fix null-ptr-deref in hugetlbfs_parse_param() |

Commit Message

Hawkins Jiawei Oct. 20, 2022, 11:16 p.m. UTC 
  Syzkaller reports a null-ptr-deref bug as follows:
======================================================
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
RIP: 0010:hugetlbfs_parse_param+0x1dd/0x8e0 fs/hugetlbfs/inode.c:1380
[...]
Call Trace:
 <TASK>
 vfs_parse_fs_param fs/fs_context.c:148 [inline]
 vfs_parse_fs_param+0x1f9/0x3c0 fs/fs_context.c:129
 vfs_parse_fs_string+0xdb/0x170 fs/fs_context.c:191
 generic_parse_monolithic+0x16f/0x1f0 fs/fs_context.c:231
 do_new_mount fs/namespace.c:3036 [inline]
 path_mount+0x12de/0x1e20 fs/namespace.c:3370
 do_mount fs/namespace.c:3383 [inline]
 __do_sys_mount fs/namespace.c:3591 [inline]
 __se_sys_mount fs/namespace.c:3568 [inline]
 __x64_sys_mount+0x27f/0x300 fs/namespace.c:3568
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
 [...]
 </TASK>
======================================================

According to commit
ac369cdd9448("vfs: parse: deal with zero length string value"),
kernel will sets the param->string to null pointer in
vfs_parse_fs_string() if fs string has zero length.

Yet the problem is that, hugetlbfs_parse_param() will
dereference the param->string, without checking whether it
is a null pointer. To be more specific, if hugetlbfs_parse_param()
parses an illegal mount parameter, such as "size=,", kernel will
constructs struct fs_parameter with null pointer in
vfs_parse_fs_string(), then passes this struct fs_parameter to
hugetlbfs_parse_param(), which triggers the above
null-ptr-deref bug.

This patch solves it by adding sanity check on param->string
in hugetlbfs_parse_param().

Reported-by: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com
Tested-by: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com
Link: https://lore.kernel.org/all/0000000000005ad00405eb7148c6@google.com/
Signed-off-by: Hawkins Jiawei <yin31149@gmail.com>
---
 fs/hugetlbfs/inode.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Comments

Mike Kravetz Oct. 20, 2022, 11:38 p.m. UTC | #1 
On 10/21/22 07:16, Hawkins Jiawei wrote:
> Syzkaller reports a null-ptr-deref bug as follows:
> ======================================================
> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> RIP: 0010:hugetlbfs_parse_param+0x1dd/0x8e0 fs/hugetlbfs/inode.c:1380
> [...]
> Call Trace:
>  <TASK>
>  vfs_parse_fs_param fs/fs_context.c:148 [inline]
>  vfs_parse_fs_param+0x1f9/0x3c0 fs/fs_context.c:129
>  vfs_parse_fs_string+0xdb/0x170 fs/fs_context.c:191
>  generic_parse_monolithic+0x16f/0x1f0 fs/fs_context.c:231
>  do_new_mount fs/namespace.c:3036 [inline]
>  path_mount+0x12de/0x1e20 fs/namespace.c:3370
>  do_mount fs/namespace.c:3383 [inline]
>  __do_sys_mount fs/namespace.c:3591 [inline]
>  __se_sys_mount fs/namespace.c:3568 [inline]
>  __x64_sys_mount+0x27f/0x300 fs/namespace.c:3568
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>  [...]
>  </TASK>
> ======================================================
> 
> According to commit
> ac369cdd9448("vfs: parse: deal with zero length string value"),
> kernel will sets the param->string to null pointer in
> vfs_parse_fs_string() if fs string has zero length.
> 
> Yet the problem is that, hugetlbfs_parse_param() will
> dereference the param->string, without checking whether it
> is a null pointer. To be more specific, if hugetlbfs_parse_param()
> parses an illegal mount parameter, such as "size=,", kernel will
> constructs struct fs_parameter with null pointer in
> vfs_parse_fs_string(), then passes this struct fs_parameter to
> hugetlbfs_parse_param(), which triggers the above
> null-ptr-deref bug.
> 
> This patch solves it by adding sanity check on param->string
> in hugetlbfs_parse_param().
> 
> Reported-by: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com
> Tested-by: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com
> Link: https://lore.kernel.org/all/0000000000005ad00405eb7148c6@google.com/
> Signed-off-by: Hawkins Jiawei <yin31149@gmail.com>

Thank you!

This was on my list of things to look at.

Do you know if the issue existed before commit ac369cdd9448?  Just
wondering if we need a Fixes tag and stable backports.

I'll take a closer look at the patch a bit later, unless someone beats
me to it.
Hawkins Jiawei Oct. 21, 2022, 2:37 a.m. UTC | #2 
Hi Mike,

On Fri, 21 Oct 2022 at 07:38, Mike Kravetz <mike.kravetz@oracle.com> wrote:
>
> On 10/21/22 07:16, Hawkins Jiawei wrote:
> > Syzkaller reports a null-ptr-deref bug as follows:
> > ======================================================
> > KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> > RIP: 0010:hugetlbfs_parse_param+0x1dd/0x8e0 fs/hugetlbfs/inode.c:1380
> > [...]
> > Call Trace:
> >  <TASK>
> >  vfs_parse_fs_param fs/fs_context.c:148 [inline]
> >  vfs_parse_fs_param+0x1f9/0x3c0 fs/fs_context.c:129
> >  vfs_parse_fs_string+0xdb/0x170 fs/fs_context.c:191
> >  generic_parse_monolithic+0x16f/0x1f0 fs/fs_context.c:231
> >  do_new_mount fs/namespace.c:3036 [inline]
> >  path_mount+0x12de/0x1e20 fs/namespace.c:3370
> >  do_mount fs/namespace.c:3383 [inline]
> >  __do_sys_mount fs/namespace.c:3591 [inline]
> >  __se_sys_mount fs/namespace.c:3568 [inline]
> >  __x64_sys_mount+0x27f/0x300 fs/namespace.c:3568
> >  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> >  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> >  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> >  [...]
> >  </TASK>
> > ======================================================
> >
> > According to commit
> > ac369cdd9448("vfs: parse: deal with zero length string value"),
> > kernel will sets the param->string to null pointer in
> > vfs_parse_fs_string() if fs string has zero length.
> >
> > Yet the problem is that, hugetlbfs_parse_param() will
> > dereference the param->string, without checking whether it
> > is a null pointer. To be more specific, if hugetlbfs_parse_param()
> > parses an illegal mount parameter, such as "size=,", kernel will
> > constructs struct fs_parameter with null pointer in
> > vfs_parse_fs_string(), then passes this struct fs_parameter to
> > hugetlbfs_parse_param(), which triggers the above
> > null-ptr-deref bug.
> >
> > This patch solves it by adding sanity check on param->string
> > in hugetlbfs_parse_param().
> >
> > Reported-by: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com
> > Tested-by: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com
> > Link: https://lore.kernel.org/all/0000000000005ad00405eb7148c6@google.com/
> > Signed-off-by: Hawkins Jiawei <yin31149@gmail.com>
>
> Thank you!
>
> This was on my list of things to look at.
>
> Do you know if the issue existed before commit ac369cdd9448?  Just
> wondering if we need a Fixes tag and stable backports.
This issue did not exist before commit ac369cdd9448, because kernel will
sets param->string a string(although a zero length string) by kmemdup_nul()
when fs string has zero length in vfs_parse_fs_string(). So it will ensures
that param->string is not a null pointer in hugetlbfs_parse_param().

I also revert commit ac369cdd9448 or reset to ac369cdd9448~, and test
the syzkaller reproducer. The reproducer does not trigger any issue
in both situations.

>
> I'll take a closer look at the patch a bit later, unless someone beats
> me to it.
> --
> Mike Kravetz
>
> > ---
> >  fs/hugetlbfs/inode.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> > index 7f836f8f9db1..3ee84604e36d 100644
> > --- a/fs/hugetlbfs/inode.c
> > +++ b/fs/hugetlbfs/inode.c
> > @@ -1377,7 +1377,7 @@ static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par
> >
> >       case Opt_size:
> >               /* memparse() will accept a K/M/G without a digit */
> > -             if (!isdigit(param->string[0]))
> > +             if (!param->string || !isdigit(param->string[0]))
> >                       goto bad_val;
> >               ctx->max_size_opt = memparse(param->string, &rest);
> >               ctx->max_val_type = SIZE_STD;
> > @@ -1387,7 +1387,7 @@ static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par
> >
> >       case Opt_nr_inodes:
> >               /* memparse() will accept a K/M/G without a digit */
> > -             if (!isdigit(param->string[0]))
> > +             if (!param->string || !isdigit(param->string[0]))
> >                       goto bad_val;
> >               ctx->nr_inodes = memparse(param->string, &rest);
> >               return 0;
> > @@ -1403,7 +1403,7 @@ static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par
> >
> >       case Opt_min_size:
> >               /* memparse() will accept a K/M/G without a digit */
> > -             if (!isdigit(param->string[0]))
> > +             if (!param->string || !isdigit(param->string[0]))
> >                       goto bad_val;
> >               ctx->min_size_opt = memparse(param->string, &rest);
> >               ctx->min_val_type = SIZE_STD;
> > --
> > 2.25.1
> >
Andrew Morton Oct. 21, 2022, 8:41 p.m. UTC | #3 
On Thu, 20 Oct 2022 16:38:18 -0700 Mike Kravetz <mike.kravetz@oracle.com> wrote:

> On 10/21/22 07:16, Hawkins Jiawei wrote:
> > Syzkaller reports a null-ptr-deref bug as follows:
> > ======================================================
> > KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> > RIP: 0010:hugetlbfs_parse_param+0x1dd/0x8e0 fs/hugetlbfs/inode.c:1380
> > [...]
> > Call Trace:
> >  <TASK>
> >  vfs_parse_fs_param fs/fs_context.c:148 [inline]
> >  vfs_parse_fs_param+0x1f9/0x3c0 fs/fs_context.c:129
> >  vfs_parse_fs_string+0xdb/0x170 fs/fs_context.c:191
> >  generic_parse_monolithic+0x16f/0x1f0 fs/fs_context.c:231
> >  do_new_mount fs/namespace.c:3036 [inline]
> >  path_mount+0x12de/0x1e20 fs/namespace.c:3370
> >  do_mount fs/namespace.c:3383 [inline]
> >  __do_sys_mount fs/namespace.c:3591 [inline]
> >  __se_sys_mount fs/namespace.c:3568 [inline]
> >  __x64_sys_mount+0x27f/0x300 fs/namespace.c:3568
> >  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> >  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> >  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> >  [...]
> >  </TASK>
> > ======================================================
> > 
> > According to commit
> > ac369cdd9448("vfs: parse: deal with zero length string value"),
> > kernel will sets the param->string to null pointer in
> > vfs_parse_fs_string() if fs string has zero length.
> > 
> > Yet the problem is that, hugetlbfs_parse_param() will
> > dereference the param->string, without checking whether it
> > is a null pointer. To be more specific, if hugetlbfs_parse_param()
> > parses an illegal mount parameter, such as "size=,", kernel will
> > constructs struct fs_parameter with null pointer in
> > vfs_parse_fs_string(), then passes this struct fs_parameter to
> > hugetlbfs_parse_param(), which triggers the above
> > null-ptr-deref bug.
> > 
> > This patch solves it by adding sanity check on param->string
> > in hugetlbfs_parse_param().
> > 
> > Reported-by: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com
> > Tested-by: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com
> > Link: https://lore.kernel.org/all/0000000000005ad00405eb7148c6@google.com/
> > Signed-off-by: Hawkins Jiawei <yin31149@gmail.com>
> 
> Thank you!
> 
> This was on my list of things to look at.
> 
> Do you know if the issue existed before commit ac369cdd9448?  Just
> wondering if we need a Fixes tag and stable backports.

Ian Kent's "vfs: parse: deal with zero length string value" exists only
in mm-nonmm-unstable.  I'm hoping that it gets some attention from Al
Viro.

I'll merge this patch so we're ready for Ian's patch.  I normally merge
mm-stable ahead of mm-nonmm-stable so there shouldn't be a bisection
window.

Ian, could you please go through the filesystems and see if there are
other instances of this getting ready to bite us?


> I'll take a closer look at the patch a bit later, unless someone beats
> me to it.
> -- 
> Mike Kravetz
> 
> > ---
> >  fs/hugetlbfs/inode.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> > index 7f836f8f9db1..3ee84604e36d 100644
> > --- a/fs/hugetlbfs/inode.c
> > +++ b/fs/hugetlbfs/inode.c
> > @@ -1377,7 +1377,7 @@ static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par
> >  
> >  	case Opt_size:
> >  		/* memparse() will accept a K/M/G without a digit */
> > -		if (!isdigit(param->string[0]))
> > +		if (!param->string || !isdigit(param->string[0]))
> >  			goto bad_val;
> >  		ctx->max_size_opt = memparse(param->string, &rest);
> >  		ctx->max_val_type = SIZE_STD;
> > @@ -1387,7 +1387,7 @@ static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par
> >  
> >  	case Opt_nr_inodes:
> >  		/* memparse() will accept a K/M/G without a digit */
> > -		if (!isdigit(param->string[0]))
> > +		if (!param->string || !isdigit(param->string[0]))
> >  			goto bad_val;
> >  		ctx->nr_inodes = memparse(param->string, &rest);
> >  		return 0;
> > @@ -1403,7 +1403,7 @@ static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par
> >  
> >  	case Opt_min_size:
> >  		/* memparse() will accept a K/M/G without a digit */
> > -		if (!isdigit(param->string[0]))
> > +		if (!param->string || !isdigit(param->string[0]))
> >  			goto bad_val;
> >  		ctx->min_size_opt = memparse(param->string, &rest);
> >  		ctx->min_val_type = SIZE_STD;
> > -- 
> > 2.25.1
> >
Mike Kravetz Oct. 22, 2022, 12:20 a.m. UTC | #4 
On 10/21/22 07:16, Hawkins Jiawei wrote:
> Syzkaller reports a null-ptr-deref bug as follows:
> ======================================================
> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> RIP: 0010:hugetlbfs_parse_param+0x1dd/0x8e0 fs/hugetlbfs/inode.c:1380
> [...]
> Call Trace:
>  <TASK>
>  vfs_parse_fs_param fs/fs_context.c:148 [inline]
>  vfs_parse_fs_param+0x1f9/0x3c0 fs/fs_context.c:129
>  vfs_parse_fs_string+0xdb/0x170 fs/fs_context.c:191
>  generic_parse_monolithic+0x16f/0x1f0 fs/fs_context.c:231
>  do_new_mount fs/namespace.c:3036 [inline]
>  path_mount+0x12de/0x1e20 fs/namespace.c:3370
>  do_mount fs/namespace.c:3383 [inline]
>  __do_sys_mount fs/namespace.c:3591 [inline]
>  __se_sys_mount fs/namespace.c:3568 [inline]
>  __x64_sys_mount+0x27f/0x300 fs/namespace.c:3568
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>  [...]
>  </TASK>
> ======================================================
> 
> According to commit
> ac369cdd9448("vfs: parse: deal with zero length string value"),
> kernel will sets the param->string to null pointer in
> vfs_parse_fs_string() if fs string has zero length.
> 
> Yet the problem is that, hugetlbfs_parse_param() will
> dereference the param->string, without checking whether it
> is a null pointer. To be more specific, if hugetlbfs_parse_param()
> parses an illegal mount parameter, such as "size=,", kernel will
> constructs struct fs_parameter with null pointer in
> vfs_parse_fs_string(), then passes this struct fs_parameter to
> hugetlbfs_parse_param(), which triggers the above
> null-ptr-deref bug.
> 
> This patch solves it by adding sanity check on param->string
> in hugetlbfs_parse_param().
> 
> Reported-by: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com
> Tested-by: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com
> Link: https://lore.kernel.org/all/0000000000005ad00405eb7148c6@google.com/
> Signed-off-by: Hawkins Jiawei <yin31149@gmail.com>
> ---
>  fs/hugetlbfs/inode.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 7f836f8f9db1..3ee84604e36d 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -1377,7 +1377,7 @@ static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par
>  
>  	case Opt_size:
>  		/* memparse() will accept a K/M/G without a digit */
> -		if (!isdigit(param->string[0]))
> +		if (!param->string || !isdigit(param->string[0]))
>  			goto bad_val;

At the bad_val label we have,

bad_val:
        return invalfc(fc, "Bad value '%s' for mount option '%s'\n",
                      param->string, param->key);

param->string still is NULL.  But, I assume the logging can handle this.
In the case of printk, a NULL pointer comes out as '(null)'.

Thanks again,

Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
diff mbox series

Patch

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 7f836f8f9db1..3ee84604e36d 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -1377,7 +1377,7 @@  static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par
 
 	case Opt_size:
 		/* memparse() will accept a K/M/G without a digit */
-		if (!isdigit(param->string[0]))
+		if (!param->string || !isdigit(param->string[0]))
 			goto bad_val;
 		ctx->max_size_opt = memparse(param->string, &rest);
 		ctx->max_val_type = SIZE_STD;
@@ -1387,7 +1387,7 @@  static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par
 
 	case Opt_nr_inodes:
 		/* memparse() will accept a K/M/G without a digit */
-		if (!isdigit(param->string[0]))
+		if (!param->string || !isdigit(param->string[0]))
 			goto bad_val;
 		ctx->nr_inodes = memparse(param->string, &rest);
 		return 0;
@@ -1403,7 +1403,7 @@  static int hugetlbfs_parse_param(struct fs_context *fc, struct fs_parameter *par
 
 	case Opt_min_size:
 		/* memparse() will accept a K/M/G without a digit */
-		if (!isdigit(param->string[0]))
+		if (!param->string || !isdigit(param->string[0]))
 			goto bad_val;
 		ctx->min_size_opt = memparse(param->string, &rest);
 		ctx->min_val_type = SIZE_STD;