general protection fault in make_kuid

general protection fault in make_kuid

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    6d21a41b Add linux-next specific files for 20190718
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15200158600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3430a151e1452331
dashboard link: https://syzkaller.appspot.com/bug?extid=7d6a57304857423318a5
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1688da20600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16de4894600000

The bug was bisected to:

commit e786741ff1b52769b044b7f4407f39cd13ee5d2d
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu Jul 11 22:36:02 2019 +0000

     Merge tag 'staging-5.3-rc1' of  
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=16610cf0600000
final crash:    https://syzkaller.appspot.com/x/report.txt?x=15610cf0600000
console output: https://syzkaller.appspot.com/x/log.txt?x=11610cf0600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+7d6a57304857423318a5@syzkaller.appspotmail.com
Fixes: e786741ff1b5 ("Merge tag 'staging-5.3-rc1' of  
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging")

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 9000 Comm: syz-executor213 Not tainted 5.2.0-next-20190718 #41
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:map_id_range_down+0x87/0x370 /kernel/user_namespace.c:293
Code: 6e 81 c7 00 f1 f1 f1 f1 c7 40 04 00 04 f3 f3 65 48 8b 04 25 28 00 00  
00 48 89 45 d0 31 c0 e8 c0 a5 03 00 4c 89 f8 48 c1 e8 03 <42> 0f b6 04 28  
84 c0 74 08 3c 03 0f 8e 9f 02 00 00 4c 8b ad 68 ff
RSP: 0018:ffff88809a567a30 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88809a567aa8 RCX: ffffffff825b97b5
RDX: 0000000000000000 RSI: ffffffff816edf30 RDI: 0000000000000000
RBP: ffff88809a567ad0 R08: ffff88808e4d2600 R09: ffffed1014af1713
R10: ffffed1014af1712 R11: 0000000000000003 R12: 0000000000000001
R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
FS:  0000555555618880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000084 CR3: 000000008b2ec000 CR4: 00000000001406f0
Call Trace:
  map_id_down /kernel/user_namespace.c:312 [inline]
  make_kuid+0x23/0x30 /kernel/user_namespace.c:389
  fuse_parse_param+0x2cb/0x750 /fs/fuse/inode.c:523
  vfs_parse_fs_param+0x2ca/0x540 /fs/fs_context.c:145
  vfs_parse_fs_string+0x105/0x170 /fs/fs_context.c:188
  generic_parse_monolithic+0x181/0x200 /fs/fs_context.c:228
  parse_monolithic_mount_data+0x69/0x90 /fs/fs_context.c:708
  do_remount /fs/namespace.c:2520 [inline]
  do_mount+0x924/0x1c30 /fs/namespace.c:3102
  ksys_mount+0xdb/0x150 /fs/namespace.c:3320
  __do_sys_mount /fs/namespace.c:3334 [inline]
  __se_sys_mount /fs/namespace.c:3331 [inline]
  __x64_sys_mount+0xbe/0x150 /fs/namespace.c:3331
  do_syscall_64+0xfd/0x6a0 /arch/x86/entry/common.c:296
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4406e9
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 5b 14 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffdf71f73c8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000007275 RCX: 00000000004406e9
RDX: 0000000000000000 RSI: 0000000020000100 RDI: 0000000000000000
RBP: 00000000006cb018 R08: 0000000020000300 R09: 65732f636f72702f
R10: 0000000000000070 R11: 0000000000000246 R12: 0000000000401fd0
R13: 0000000000402060 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace 4fbbc963024437d2 ]---
RIP: 0010:map_id_range_down+0x87/0x370 /kernel/user_namespace.c:293
Code: 6e 81 c7 00 f1 f1 f1 f1 c7 40 04 00 04 f3 f3 65 48 8b 04 25 28 00 00  
00 48 89 45 d0 31 c0 e8 c0 a5 03 00 4c 89 f8 48 c1 e8 03 <42> 0f b6 04 28  
84 c0 74 08 3c 03 0f 8e 9f 02 00 00 4c 8b ad 68 ff
RSP: 0018:ffff88809a567a30 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88809a567aa8 RCX: ffffffff825b97b5
RDX: 0000000000000000 RSI: ffffffff816edf30 RDI: 0000000000000000
RBP: ffff88809a567ad0 R08: ffff88808e4d2600 R09: ffffed1014af1713
R10: ffffed1014af1712 R11: 0000000000000003 R12: 0000000000000001
R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000
FS:  0000555555618880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000084 CR3: 000000008b2ec000 CR4: 00000000001406f0


---
This bug is generated by a bot. It may contain errors.
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

[PATCH] vfs: set fs_context::user_ns for reconfigure

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

fs_context::user_ns is used by fuse_parse_param(), even during remount,
so it needs to be set to the existing value for reconfigure.

Reproducer:

	#include <fcntl.h>
	#include <sys/mount.h>

	int main()
	{
		char opts[128];
		int fd = open("/dev/fuse", O_RDWR);

		sprintf(opts, "fd=%d,rootmode=040000,user_id=0,group_id=0", fd);
		mkdir("mnt", 0777);
		mount("foo",  "mnt", "fuse.foo", 0, opts);
		mount("foo", "mnt", "fuse.foo", MS_REMOUNT, opts);
	}

Crash:
	BUG: kernel NULL pointer dereference, address: 0000000000000000
	#PF: supervisor read access in kernel mode
	#PF: error_code(0x0000) - not-present page
	PGD 0 P4D 0
	Oops: 0000 [#1] SMP
	CPU: 0 PID: 129 Comm: syz_make_kuid Not tainted 5.3.0-rc5-next-20190821 #3
	Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-20181126_142135-anatol 04/01/2014
	RIP: 0010:map_id_range_down+0xb/0xc0 kernel/user_namespace.c:291
	[...]
	Call Trace:
	 map_id_down kernel/user_namespace.c:312 [inline]
	 make_kuid+0xe/0x10 kernel/user_namespace.c:389
	 fuse_parse_param+0x116/0x210 fs/fuse/inode.c:523
	 vfs_parse_fs_param+0xdb/0x1b0 fs/fs_context.c:145
	 vfs_parse_fs_string+0x6a/0xa0 fs/fs_context.c:188
	 generic_parse_monolithic+0x85/0xc0 fs/fs_context.c:228
	 parse_monolithic_mount_data+0x1b/0x20 fs/fs_context.c:708
	 do_remount fs/namespace.c:2525 [inline]
	 do_mount+0x39a/0xa60 fs/namespace.c:3107
	 ksys_mount+0x7d/0xd0 fs/namespace.c:3325
	 __do_sys_mount fs/namespace.c:3339 [inline]
	 __se_sys_mount fs/namespace.c:3336 [inline]
	 __x64_sys_mount+0x20/0x30 fs/namespace.c:3336
	 do_syscall_64+0x4a/0x1a0 arch/x86/entry/common.c:290
	 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Reported-by: syzbot+7d6a57304857423318a5@syzkaller.appspotmail.com
Fixes: 408cbe695350 ("vfs: Convert fuse to use the new mount API")
Cc: David Howells <dhowells@redhat.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/fs_context.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/fs_context.c b/fs/fs_context.c
index cc61d305dc4b..44c4174b250a 100644
--- a/fs/fs_context.c
+++ b/fs/fs_context.c
@@ -279,10 +279,8 @@ static struct fs_context *alloc_fs_context(struct file_system_type *fs_type,
 		fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
 		break;
 	case FS_CONTEXT_FOR_RECONFIGURE:
-		/* We don't pin any namespaces as the superblock's
-		 * subscriptions cannot be changed at this point.
-		 */
 		atomic_inc(&reference->d_sb->s_active);
+		fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
 		fc->root = dget(reference);
 		break;
 	}
-- 
2.22.1

Re: [PATCH] vfs: set fs_context::user_ns for reconfigure

[Eric Biggers]

On Wed, Aug 21, 2019 at 10:16:33PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> fs_context::user_ns is used by fuse_parse_param(), even during remount,
> so it needs to be set to the existing value for reconfigure.
> 
> Reproducer:
> 
> 	#include <fcntl.h>
> 	#include <sys/mount.h>
> 
> 	int main()
> 	{
> 		char opts[128];
> 		int fd = open("/dev/fuse", O_RDWR);
> 
> 		sprintf(opts, "fd=%d,rootmode=040000,user_id=0,group_id=0", fd);
> 		mkdir("mnt", 0777);
> 		mount("foo",  "mnt", "fuse.foo", 0, opts);
> 		mount("foo", "mnt", "fuse.foo", MS_REMOUNT, opts);
> 	}
> 
> Crash:
> 	BUG: kernel NULL pointer dereference, address: 0000000000000000
> 	#PF: supervisor read access in kernel mode
> 	#PF: error_code(0x0000) - not-present page
> 	PGD 0 P4D 0
> 	Oops: 0000 [#1] SMP
> 	CPU: 0 PID: 129 Comm: syz_make_kuid Not tainted 5.3.0-rc5-next-20190821 #3
> 	Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-20181126_142135-anatol 04/01/2014
> 	RIP: 0010:map_id_range_down+0xb/0xc0 kernel/user_namespace.c:291
> 	[...]
> 	Call Trace:
> 	 map_id_down kernel/user_namespace.c:312 [inline]
> 	 make_kuid+0xe/0x10 kernel/user_namespace.c:389
> 	 fuse_parse_param+0x116/0x210 fs/fuse/inode.c:523
> 	 vfs_parse_fs_param+0xdb/0x1b0 fs/fs_context.c:145
> 	 vfs_parse_fs_string+0x6a/0xa0 fs/fs_context.c:188
> 	 generic_parse_monolithic+0x85/0xc0 fs/fs_context.c:228
> 	 parse_monolithic_mount_data+0x1b/0x20 fs/fs_context.c:708
> 	 do_remount fs/namespace.c:2525 [inline]
> 	 do_mount+0x39a/0xa60 fs/namespace.c:3107
> 	 ksys_mount+0x7d/0xd0 fs/namespace.c:3325
> 	 __do_sys_mount fs/namespace.c:3339 [inline]
> 	 __se_sys_mount fs/namespace.c:3336 [inline]
> 	 __x64_sys_mount+0x20/0x30 fs/namespace.c:3336
> 	 do_syscall_64+0x4a/0x1a0 arch/x86/entry/common.c:290
> 	 entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> Reported-by: syzbot+7d6a57304857423318a5@syzkaller.appspotmail.com
> Fixes: 408cbe695350 ("vfs: Convert fuse to use the new mount API")
> Cc: David Howells <dhowells@redhat.com>
> Cc: Miklos Szeredi <miklos@szeredi.hu>
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  fs/fs_context.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/fs/fs_context.c b/fs/fs_context.c
> index cc61d305dc4b..44c4174b250a 100644
> --- a/fs/fs_context.c
> +++ b/fs/fs_context.c
> @@ -279,10 +279,8 @@ static struct fs_context *alloc_fs_context(struct file_system_type *fs_type,
>  		fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
>  		break;
>  	case FS_CONTEXT_FOR_RECONFIGURE:
> -		/* We don't pin any namespaces as the superblock's
> -		 * subscriptions cannot be changed at this point.
> -		 */
>  		atomic_inc(&reference->d_sb->s_active);
> +		fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
>  		fc->root = dget(reference);
>  		break;
>  	}
> -- 
> 2.22.1

Ping.

Re: [PATCH] vfs: set fs_context::user_ns for reconfigure

[Eric Biggers]

On Fri, Aug 30, 2019 at 10:12:28PM -0500, Eric Biggers wrote:
> On Wed, Aug 21, 2019 at 10:16:33PM -0700, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@google.com>
> > 
> > fs_context::user_ns is used by fuse_parse_param(), even during remount,
> > so it needs to be set to the existing value for reconfigure.
> > 
> > Reproducer:
> > 
> > 	#include <fcntl.h>
> > 	#include <sys/mount.h>
> > 
> > 	int main()
> > 	{
> > 		char opts[128];
> > 		int fd = open("/dev/fuse", O_RDWR);
> > 
> > 		sprintf(opts, "fd=%d,rootmode=040000,user_id=0,group_id=0", fd);
> > 		mkdir("mnt", 0777);
> > 		mount("foo",  "mnt", "fuse.foo", 0, opts);
> > 		mount("foo", "mnt", "fuse.foo", MS_REMOUNT, opts);
> > 	}
> > 
> > Crash:
> > 	BUG: kernel NULL pointer dereference, address: 0000000000000000
> > 	#PF: supervisor read access in kernel mode
> > 	#PF: error_code(0x0000) - not-present page
> > 	PGD 0 P4D 0
> > 	Oops: 0000 [#1] SMP
> > 	CPU: 0 PID: 129 Comm: syz_make_kuid Not tainted 5.3.0-rc5-next-20190821 #3
> > 	Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-20181126_142135-anatol 04/01/2014
> > 	RIP: 0010:map_id_range_down+0xb/0xc0 kernel/user_namespace.c:291
> > 	[...]
> > 	Call Trace:
> > 	 map_id_down kernel/user_namespace.c:312 [inline]
> > 	 make_kuid+0xe/0x10 kernel/user_namespace.c:389
> > 	 fuse_parse_param+0x116/0x210 fs/fuse/inode.c:523
> > 	 vfs_parse_fs_param+0xdb/0x1b0 fs/fs_context.c:145
> > 	 vfs_parse_fs_string+0x6a/0xa0 fs/fs_context.c:188
> > 	 generic_parse_monolithic+0x85/0xc0 fs/fs_context.c:228
> > 	 parse_monolithic_mount_data+0x1b/0x20 fs/fs_context.c:708
> > 	 do_remount fs/namespace.c:2525 [inline]
> > 	 do_mount+0x39a/0xa60 fs/namespace.c:3107
> > 	 ksys_mount+0x7d/0xd0 fs/namespace.c:3325
> > 	 __do_sys_mount fs/namespace.c:3339 [inline]
> > 	 __se_sys_mount fs/namespace.c:3336 [inline]
> > 	 __x64_sys_mount+0x20/0x30 fs/namespace.c:3336
> > 	 do_syscall_64+0x4a/0x1a0 arch/x86/entry/common.c:290
> > 	 entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > 
> > Reported-by: syzbot+7d6a57304857423318a5@syzkaller.appspotmail.com
> > Fixes: 408cbe695350 ("vfs: Convert fuse to use the new mount API")
> > Cc: David Howells <dhowells@redhat.com>
> > Cc: Miklos Szeredi <miklos@szeredi.hu>
> > Signed-off-by: Eric Biggers <ebiggers@google.com>
> > ---
> >  fs/fs_context.c | 4 +---
> >  1 file changed, 1 insertion(+), 3 deletions(-)
> > 
> > diff --git a/fs/fs_context.c b/fs/fs_context.c
> > index cc61d305dc4b..44c4174b250a 100644
> > --- a/fs/fs_context.c
> > +++ b/fs/fs_context.c
> > @@ -279,10 +279,8 @@ static struct fs_context *alloc_fs_context(struct file_system_type *fs_type,
> >  		fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
> >  		break;
> >  	case FS_CONTEXT_FOR_RECONFIGURE:
> > -		/* We don't pin any namespaces as the superblock's
> > -		 * subscriptions cannot be changed at this point.
> > -		 */
> >  		atomic_inc(&reference->d_sb->s_active);
> > +		fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
> >  		fc->root = dget(reference);
> >  		break;
> >  	}
> > -- 
> > 2.22.1
> 
> Ping.
> 

Ping.  This is still broken in linux-next.

- Eric