[syzbot] [fuse?] general protection fault in fuse_do_readpage

[syzbot] [fuse?] general protection fault in fuse_do_readpage

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    c1e939a21eb1 Merge tag 'cgroup-for-6.12-rc5-fixes' of git:..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=173f255f980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4340261e4e9f37fc
dashboard link: https://syzkaller.appspot.com/bug?extid=0b1279812c46e48bb0c1
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12401540580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10e64630580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7feb34a89c2a/non_bootable_disk-c1e939a2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5f1b9c52b9e0/vmlinux-c1e939a2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8f31f28c172e/bzImage-c1e939a2.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0b1279812c46e48bb0c1@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc000000000c: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000060-0x0000000000000067]
CPU: 3 UID: 0 PID: 5947 Comm: syz-executor314 Not tainted 6.12.0-rc5-syzkaller-00044-gc1e939a21eb1 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:fuse_read_args_fill fs/fuse/file.c:631 [inline]
RIP: 0010:fuse_do_readpage+0x276/0x640 fs/fuse/file.c:880
Code: e8 9f c7 91 fe 8b 44 24 10 89 44 24 78 41 89 c4 e8 8f c7 91 fe 48 8d 7b 60 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 1d 03 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b
RSP: 0018:ffffc90006a0f820 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff82fbb4c9
RDX: 000000000000000c RSI: ffffffff82fbb4f1 RDI: 0000000000000060
RBP: 0000000000000000 R08: 0000000000000007 R09: 7fffffffffffffff
R10: 0000000000000fff R11: ffffffff961d4b88 R12: 0000000000001000
R13: ffff8880382b8000 R14: ffff888025153780 R15: ffffc90006a0f8b8
FS:  00007f7583f3d6c0(0000) GS:ffff88806a900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000240 CR3: 0000000030d30000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 fuse_read_folio+0xb0/0x100 fs/fuse/file.c:905
 filemap_read_folio+0xc6/0x2a0 mm/filemap.c:2367
 do_read_cache_folio+0x263/0x5c0 mm/filemap.c:3825
 read_mapping_folio include/linux/pagemap.h:1011 [inline]
 erofs_bread+0x34d/0x7e0 fs/erofs/data.c:41
 erofs_read_superblock fs/erofs/super.c:281 [inline]
 erofs_fc_fill_super+0x2b9/0x2500 fs/erofs/super.c:625
 vfs_get_super fs/super.c:1280 [inline]
 get_tree_nodev+0xda/0x190 fs/super.c:1299
 erofs_fc_get_tree+0x1fe/0x2e0 fs/erofs/super.c:723
 vfs_get_tree+0x8f/0x380 fs/super.c:1800
 do_new_mount fs/namespace.c:3507 [inline]
 path_mount+0x14e6/0x1f20 fs/namespace.c:3834
 do_mount fs/namespace.c:3847 [inline]
 __do_sys_mount fs/namespace.c:4057 [inline]
 __se_sys_mount fs/namespace.c:4034 [inline]
 __x64_sys_mount+0x294/0x320 fs/namespace.c:4034
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7583f813b9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 00 00 90 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 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f7583f3d218 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f758400d3e8 RCX: 00007f7583f813b9
RDX: 00000000200000c0 RSI: 0000000020000000 RDI: 0000000020000240
RBP: 00007f758400d3e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000010000 R11: 0000000000000246 R12: 00007f7583fda034
R13: 0030656c69662f2e R14: 00007f7583fda050 R15: 00007f7583fd800e
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:fuse_read_args_fill fs/fuse/file.c:631 [inline]
RIP: 0010:fuse_do_readpage+0x276/0x640 fs/fuse/file.c:880
Code: e8 9f c7 91 fe 8b 44 24 10 89 44 24 78 41 89 c4 e8 8f c7 91 fe 48 8d 7b 60 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 1d 03 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b
RSP: 0018:ffffc90006a0f820 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff82fbb4c9
RDX: 000000000000000c RSI: ffffffff82fbb4f1 RDI: 0000000000000060
RBP: 0000000000000000 R08: 0000000000000007 R09: 7fffffffffffffff
R10: 0000000000000fff R11: ffffffff961d4b88 R12: 0000000000001000
R13: ffff8880382b8000 R14: ffff888025153780 R15: ffffc90006a0f8b8
FS:  00007f7583f3d6c0(0000) GS:ffff88806a900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000240 CR3: 0000000030d30000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	e8 9f c7 91 fe       	call   0xfe91c7a4
   5:	8b 44 24 10          	mov    0x10(%rsp),%eax
   9:	89 44 24 78          	mov    %eax,0x78(%rsp)
   d:	41 89 c4             	mov    %eax,%r12d
  10:	e8 8f c7 91 fe       	call   0xfe91c7a4
  15:	48 8d 7b 60          	lea    0x60(%rbx),%rdi
  19:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  20:	fc ff df
  23:	48 89 fa             	mov    %rdi,%rdx
  26:	48 c1 ea 03          	shr    $0x3,%rdx
* 2a:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
  2e:	0f 85 1d 03 00 00    	jne    0x351
  34:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  3b:	fc ff df
  3e:	48                   	rex.W
  3f:	8b                   	.byte 0x8b


---
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Re: [syzbot] [fuse?] general protection fault in fuse_do_readpage

[Lizhi Xu]

about this case, calltrace is:
erofs_read_superblock()->
	erofs_read_metabuf()->
		erofs_bread()->
			read_mapping_folio()
	
41                  folio = read_mapping_folio(buf->mapping, index, NULL);
file is NULL in read_mapping_folio() at fs/erofs/data.c, and in fuse_do_readpage(),
it need file pass node id and file handle(in userspace), so need to add a
check for file in fuse_read_folio().

#syz test

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index f33fbce86ae0..fe6df701da24 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -902,6 +902,9 @@ static int fuse_read_folio(struct file *file, struct folio *folio)
 	if (fuse_is_bad(inode))
 		goto out;
 
+	if (!file)
+		goto out;
+
 	err = fuse_do_readpage(file, page);
 	fuse_invalidate_atime(inode);
  out:

Re: [syzbot] [fuse?] general protection fault in fuse_do_readpage

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+0b1279812c46e48bb0c1@syzkaller.appspotmail.com
Tested-by: syzbot+0b1279812c46e48bb0c1@syzkaller.appspotmail.com

Tested on:

commit:         59b723cd Linux 6.12-rc6
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15127630580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2effb62852f5a821
dashboard link: https://syzkaller.appspot.com/bug?extid=0b1279812c46e48bb0c1
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=10827630580000

Note: testing is done by a robot and is best-effort only.

[PATCH] fuse: check file before running readpage

[Lizhi Xu]

syzbot reported a null-ptr-deref in fuse_read_args_fill. [1]

About this case, calltrace is:
erofs_read_superblock()->
  erofs_read_metabuf()->
    erofs_bread()->
      read_mapping_folio()->
        do_read_cache_folio()->
          filemap_read_folio()->
            fuse_read_folio()->
              fuse_do_readpage()->
                fuse_read_args_fill()

erofs_bread() calls read_mapping_folio() passing NULL file, which causes a
NULL pointer dereference in fuse_read_args_fill.
To avoid this issue, need to add a check for file in fuse_read_folio().

[1]
KASAN: null-ptr-deref in range [0x0000000000000060-0x0000000000000067]
CPU: 3 UID: 0 PID: 5947 Comm: syz-executor314 Not tainted 6.12.0-rc5-syzkaller-00044-gc1e939a21eb1 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:fuse_read_args_fill fs/fuse/file.c:631 [inline]
RIP: 0010:fuse_do_readpage+0x276/0x640 fs/fuse/file.c:880
Code: e8 9f c7 91 fe 8b 44 24 10 89 44 24 78 41 89 c4 e8 8f c7 91 fe 48 8d 7b 60 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 1d 03 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b
RSP: 0018:ffffc90006a0f820 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff82fbb4c9
RDX: 000000000000000c RSI: ffffffff82fbb4f1 RDI: 0000000000000060
RBP: 0000000000000000 R08: 0000000000000007 R09: 7fffffffffffffff
R10: 0000000000000fff R11: ffffffff961d4b88 R12: 0000000000001000
R13: ffff8880382b8000 R14: ffff888025153780 R15: ffffc90006a0f8b8
FS:  00007f7583f3d6c0(0000) GS:ffff88806a900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000240 CR3: 0000000030d30000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 fuse_read_folio+0xb0/0x100 fs/fuse/file.c:905
 filemap_read_folio+0xc6/0x2a0 mm/filemap.c:2367
 do_read_cache_folio+0x263/0x5c0 mm/filemap.c:3825
 read_mapping_folio include/linux/pagemap.h:1011 [inline]
 erofs_bread+0x34d/0x7e0 fs/erofs/data.c:41
 erofs_read_superblock fs/erofs/super.c:281 [inline]
 erofs_fc_fill_super+0x2b9/0x2500 fs/erofs/super.c:625
 vfs_get_super fs/super.c:1280 [inline]
 get_tree_nodev+0xda/0x190 fs/super.c:1299
 erofs_fc_get_tree+0x1fe/0x2e0 fs/erofs/super.c:723
 vfs_get_tree+0x8f/0x380 fs/super.c:1800
 do_new_mount fs/namespace.c:3507 [inline]
 path_mount+0x14e6/0x1f20 fs/namespace.c:3834
 do_mount fs/namespace.c:3847 [inline]
 __do_sys_mount fs/namespace.c:4057 [inline]
 __se_sys_mount fs/namespace.c:4034 [inline]
 __x64_sys_mount+0x294/0x320 fs/namespace.c:4034
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported-and-tested-by: syzbot+0b1279812c46e48bb0c1@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=0b1279812c46e48bb0c1
Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
---
 fs/fuse/file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index dafdf766b1d5..5ce37d1f617c 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -899,7 +899,7 @@ static int fuse_read_folio(struct file *file, struct folio *folio)
 	int err;
 
 	err = -EIO;
-	if (fuse_is_bad(inode))
+	if (fuse_is_bad(inode) || !file)
 		goto out;
 
 	err = fuse_do_readpage(file, page);
-- 
2.43.0

Re: [PATCH] fuse: check file before running readpage

[Gao Xiang]

On 2024/11/14 10:04, Lizhi Xu wrote:
> syzbot reported a null-ptr-deref in fuse_read_args_fill. [1]
> 
> About this case, calltrace is:
> erofs_read_superblock()->
>    erofs_read_metabuf()->
>      erofs_bread()->
>        read_mapping_folio()->
>          do_read_cache_folio()->
>            filemap_read_folio()->
>              fuse_read_folio()->
>                fuse_do_readpage()->
>                  fuse_read_args_fill()
> 
> erofs_bread() calls read_mapping_folio() passing NULL file, which causes a
> NULL pointer dereference in fuse_read_args_fill.
> To avoid this issue, need to add a check for file in fuse_read_folio().
> 
> [1]
> KASAN: null-ptr-deref in range [0x0000000000000060-0x0000000000000067]
> CPU: 3 UID: 0 PID: 5947 Comm: syz-executor314 Not tainted 6.12.0-rc5-syzkaller-00044-gc1e939a21eb1 #0
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
> RIP: 0010:fuse_read_args_fill fs/fuse/file.c:631 [inline]
> RIP: 0010:fuse_do_readpage+0x276/0x640 fs/fuse/file.c:880
> Code: e8 9f c7 91 fe 8b 44 24 10 89 44 24 78 41 89 c4 e8 8f c7 91 fe 48 8d 7b 60 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 1d 03 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b
> RSP: 0018:ffffc90006a0f820 EFLAGS: 00010206
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff82fbb4c9
> RDX: 000000000000000c RSI: ffffffff82fbb4f1 RDI: 0000000000000060
> RBP: 0000000000000000 R08: 0000000000000007 R09: 7fffffffffffffff
> R10: 0000000000000fff R11: ffffffff961d4b88 R12: 0000000000001000
> R13: ffff8880382b8000 R14: ffff888025153780 R15: ffffc90006a0f8b8
> FS:  00007f7583f3d6c0(0000) GS:ffff88806a900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020000240 CR3: 0000000030d30000 CR4: 0000000000352ef0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   <TASK>
>   fuse_read_folio+0xb0/0x100 fs/fuse/file.c:905
>   filemap_read_folio+0xc6/0x2a0 mm/filemap.c:2367
>   do_read_cache_folio+0x263/0x5c0 mm/filemap.c:3825
>   read_mapping_folio include/linux/pagemap.h:1011 [inline]
>   erofs_bread+0x34d/0x7e0 fs/erofs/data.c:41
>   erofs_read_superblock fs/erofs/super.c:281 [inline]
>   erofs_fc_fill_super+0x2b9/0x2500 fs/erofs/super.c:625
>   vfs_get_super fs/super.c:1280 [inline]
>   get_tree_nodev+0xda/0x190 fs/super.c:1299
>   erofs_fc_get_tree+0x1fe/0x2e0 fs/erofs/super.c:723
>   vfs_get_tree+0x8f/0x380 fs/super.c:1800
>   do_new_mount fs/namespace.c:3507 [inline]
>   path_mount+0x14e6/0x1f20 fs/namespace.c:3834
>   do_mount fs/namespace.c:3847 [inline]
>   __do_sys_mount fs/namespace.c:4057 [inline]
>   __se_sys_mount fs/namespace.c:4034 [inline]
>   __x64_sys_mount+0x294/0x320 fs/namespace.c:4034
>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>   do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
> 
> Reported-and-tested-by: syzbot+0b1279812c46e48bb0c1@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=0b1279812c46e48bb0c1
> Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>

Most filesystems (except for some network fses and FUSE)
won't use `file` at all and as documented in
https://docs.kernel.org/filesystems/vfs.html

But I will pass in `file` for this issue instead in order
to support use cases over FUSE, other than just bail out
like this.

Thanks,
Gao Xiang

Re: [syzbot] [fuse?] general protection fault in fuse_do_readpage

[Gao Xiang]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git dev-test

Re: [syzbot] [fuse?] general protection fault in fuse_do_readpage

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+0b1279812c46e48bb0c1@syzkaller.appspotmail.com
Tested-by: syzbot+0b1279812c46e48bb0c1@syzkaller.appspotmail.com

Tested on:

commit:         779014de erofs: fix file-backed mounts over FUSE
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git dev-test
console output: https://syzkaller.appspot.com/x/log.txt?x=155294c0580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2effb62852f5a821
dashboard link: https://syzkaller.appspot.com/bug?extid=0b1279812c46e48bb0c1
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.