[syzbot] [mm?] general protection fault in mas_start

[syzbot] [mm?] general protection fault in mas_start

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    a62b7a37e6fc Add linux-next specific files for 20250711
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15d45d82580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=bb4e3ec360fcbd0f
dashboard link: https://syzkaller.appspot.com/bug?extid=ffe421482ad9d307c03f
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1177018c580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1577018c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7965e5d0fd00/disk-a62b7a37.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d3f74e66ef93/vmlinux-a62b7a37.xz
kernel image: https://storage.googleapis.com/syzbot-assets/90b196a2a6e8/bzImage-a62b7a37.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ffe421482ad9d307c03f@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000009: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000048-0x000000000000004f]
CPU: 0 UID: 0 PID: 6062 Comm: syz.0.19 Not tainted 6.16.0-rc5-next-20250711-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:mas_root lib/maple_tree.c:844 [inline]
RIP: 0010:mas_start+0x10c/0x560 lib/maple_tree.c:1377
Code: 85 4e 02 00 00 c6 43 3c 00 48 8b 44 24 30 80 3c 28 00 74 08 48 89 df e8 f2 1b b3 f6 4c 8b 33 49 83 c6 48 4c 89 f0 48 c1 e8 03 <80> 3c 28 00 74 08 4c 89 f7 e8 d6 1b b3 f6 4d 8b 26 e8 fe ec 08 00
RSP: 0018:ffffc90003367a08 EFLAGS: 00010206

RAX: 0000000000000009 RBX: ffff8880762e8d18 RCX: 1ffff1100ec5d1aa
RDX: 1ffff1100ec5d1aa RSI: 0000000000000001 RDI: ffff8880762e8d40
RBP: dffffc0000000000 R08: ffff88801dfd1e00 R09: 0000000000000006
R10: 0000000000000007 R11: 0000000000000000 R12: 0000200001000000
R13: ffff8880762e8d30 R14: 0000000000000048 R15: ffff8880762e8d50
FS:  00007ff7b5a9d6c0(0000) GS:ffff888125bc6000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff7b5a9cf98 CR3: 000000007604c000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 mas_state_walk lib/maple_tree.c:3629 [inline]
 mas_walk lib/maple_tree.c:4939 [inline]
 mas_find_setup lib/maple_tree.c:6018 [inline]
 mas_find+0x8aa/0xd30 lib/maple_tree.c:6058
 vma_next include/linux/mm.h:864 [inline]
 lock_next_vma+0x101/0xdc0 mm/mmap_lock.c:216
 get_next_vma fs/proc/task_mmu.c:182 [inline]
 query_vma_find_by_addr fs/proc/task_mmu.c:512 [inline]
 query_matching_vma+0x319/0x5c0 fs/proc/task_mmu.c:544
 do_procmap_query fs/proc/task_mmu.c:629 [inline]
 procfs_procmap_ioctl+0x3f9/0xd50 fs/proc/task_mmu.c:747
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:598 [inline]
 __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:584
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff7b4b8e929
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff7b5a9d038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ff7b4db6080 RCX: 00007ff7b4b8e929
RDX: 0000200000000180 RSI: 00000000c0686611 RDI: 0000000000000003
RBP: 00007ff7b4c10b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007ff7b4db6080 R15: 00007ffde30986a8
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:mas_root lib/maple_tree.c:844 [inline]
RIP: 0010:mas_start+0x10c/0x560 lib/maple_tree.c:1377
Code: 85 4e 02 00 00 c6 43 3c 00 48 8b 44 24 30 80 3c 28 00 74 08 48 89 df e8 f2 1b b3 f6 4c 8b 33 49 83 c6 48 4c 89 f0 48 c1 e8 03 <80> 3c 28 00 74 08 4c 89 f7 e8 d6 1b b3 f6 4d 8b 26 e8 fe ec 08 00
RSP: 0018:ffffc90003367a08 EFLAGS: 00010206
RAX: 0000000000000009 RBX: ffff8880762e8d18 RCX: 1ffff1100ec5d1aa
RDX: 1ffff1100ec5d1aa RSI: 0000000000000001 RDI: ffff8880762e8d40
RBP: dffffc0000000000 R08: ffff88801dfd1e00 R09: 0000000000000006
R10: 0000000000000007 R11: 0000000000000000 R12: 0000200001000000
R13: ffff8880762e8d30 R14: 0000000000000048 R15: ffff8880762e8d50
FS:  00007ff7b5a9d6c0(0000) GS:ffff888125bc6000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff7b5a9cf98 CR3: 000000007604c000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	85 4e 02             	test   %ecx,0x2(%rsi)
   3:	00 00                	add    %al,(%rax)
   5:	c6 43 3c 00          	movb   $0x0,0x3c(%rbx)
   9:	48 8b 44 24 30       	mov    0x30(%rsp),%rax
   e:	80 3c 28 00          	cmpb   $0x0,(%rax,%rbp,1)
  12:	74 08                	je     0x1c
  14:	48 89 df             	mov    %rbx,%rdi
  17:	e8 f2 1b b3 f6       	call   0xf6b31c0e
  1c:	4c 8b 33             	mov    (%rbx),%r14
  1f:	49 83 c6 48          	add    $0x48,%r14
  23:	4c 89 f0             	mov    %r14,%rax
  26:	48 c1 e8 03          	shr    $0x3,%rax
* 2a:	80 3c 28 00          	cmpb   $0x0,(%rax,%rbp,1) <-- trapping instruction
  2e:	74 08                	je     0x38
  30:	4c 89 f7             	mov    %r14,%rdi
  33:	e8 d6 1b b3 f6       	call   0xf6b31c0e
  38:	4d 8b 26             	mov    (%r14),%r12
  3b:	e8 fe ec 08 00       	call   0x8ed3e


---
This report is generated by a bot. It may contain errors.
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#syz test: git://repo/address.git branch-or-commit-hash
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Re: [syzbot] [mm?] general protection fault in mas_start

[Hillf Danton]

> Date: Mon, 14 Jul 2025 10:09:31 -0700	[thread overview]
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    a62b7a37e6fc Add linux-next specific files for 20250711
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=15d45d82580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=bb4e3ec360fcbd0f
> dashboard link: https://syzkaller.appspot.com/bug?extid=ffe421482ad9d307c03f
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1177018c580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1577018c580000

#syz test

--- x/fs/proc/task_mmu.c
+++ y/fs/proc/task_mmu.c
@@ -585,6 +585,7 @@ no_vma:
 	return ERR_PTR(-ENOENT);
 }
 
+static DEFINE_MUTEX(query_mutex);
 static int do_procmap_query(struct proc_maps_private *priv, void __user *uarg)
 {
 	struct procmap_query karg;
@@ -620,8 +621,10 @@ static int do_procmap_query(struct proc_
 	if (!mm || !mmget_not_zero(mm))
 		return -ESRCH;
 
+	mutex_lock(&query_mutex);
 	err = query_vma_setup(priv);
 	if (err) {
+		mutex_unlock(&query_mutex);
 		mmput(mm);
 		return err;
 	}
@@ -712,6 +715,7 @@ static int do_procmap_query(struct proc_
 
 	/* unlock vma or mmap_lock, and put mm_struct before copying data to user */
 	query_vma_teardown(priv);
+	mutex_unlock(&query_mutex);
 	mmput(mm);
 
 	if (karg.vma_name_size && copy_to_user(u64_to_user_ptr(karg.vma_name_addr),
@@ -732,6 +736,7 @@ static int do_procmap_query(struct proc_
 
 out:
 	query_vma_teardown(priv);
+	mutex_unlock(&query_mutex);
 	mmput(mm);
 	kfree(name_buf);
 	return err;
--

Re: [syzbot] [mm?] general protection fault in mas_start

[syzbot]

Hello,

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

Reported-by: syzbot+ffe421482ad9d307c03f@syzkaller.appspotmail.com
Tested-by: syzbot+ffe421482ad9d307c03f@syzkaller.appspotmail.com

Tested on:

commit:         0be23810 Add linux-next specific files for 20250714
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=10c5518c580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=adc3ea2bfe31343b
dashboard link: https://syzkaller.appspot.com/bug?extid=ffe421482ad9d307c03f
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
patch:          https://syzkaller.appspot.com/x/patch.diff?x=17a9518c580000

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