Dear developers and maintainers, We encountered a general protection fault in udmabuf_create. It is tested on latest upstream linux (6.9-rc3). The kernel log is listed below. ``` general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f] CPU: 0 PID: 8122 Comm: syz-executor422 Not tainted 6.7.0-rc7 #2 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 RIP: 0010:udmabuf_create+0x220/0xe60 drivers/dma-buf/udmabuf.c:217 Code: 83 c5 18 44 89 e7 e8 cf 73 04 fc 45 39 fc 0f 84 fe 00 00 00 e8 21 78 04 fc 48 89 e8 48 b9 00 00 00 00 00 fc ff df 48 c1 e8 03 <80> 3c 08 00 0f 85 d6 08 00 00 48 8b 5d 00 31 ff 81 e3 ff 0f 00 00 RSP: 0018:ffffc90002a2fca8 EFLAGS: 00010206 RAX: 0000000000000003 RBX: dffffc0000000000 RCX: dffffc0000000000 RDX: ffff8881074a4980 RSI: ffffffff85809cef RDI: 0000000000000005 RBP: 0000000000000018 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000080000000 R11: ffffffff8a80008b R12: 0000000000000000 R13: 0000000000004000 R14: ffff8880162ec380 R15: 0000000080000000 FS: 0000555556e1b3c0(0000) GS:ffff888063a00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020000000 CR3: 000000001b7ab000 CR4: 0000000000750ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: <TASK> udmabuf_ioctl_create_list drivers/dma-buf/udmabuf.c:328 [inline] udmabuf_ioctl+0x26d/0x2c0 drivers/dma-buf/udmabuf.c:343 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:871 [inline] __se_sys_ioctl fs/ioctl.c:857 [inline] __x64_sys_ioctl+0x19d/0x210 fs/ioctl.c:857 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0x40/0x110 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x63/0x6b RIP: 0033:0x7fd8fab06b4d Code: 28 c3 e8 46 1e 00 00 66 0f 1f 44 00 00 f3 0f 1e fa 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 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fffb972c428 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fffb972c628 RCX: 00007fd8fab06b4d RDX: 0000000020000000 RSI: 0000000040087543 RDI: 0000000000000003 RBP: 0000000000000001 R08: 0074696d696c5f74 R09: 00007fffb972c628 R10: 000000000000000f R11: 0000000000000246 R12: 0000000000000001 R13: 00007fffb972c618 R14: 00007fd8fab84530 R15: 0000000000000001 </TASK> Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:udmabuf_create+0x220/0xe60 drivers/dma-buf/udmabuf.c:217 Code: 83 c5 18 44 89 e7 e8 cf 73 04 fc 45 39 fc 0f 84 fe 00 00 00 e8 21 78 04 fc 48 89 e8 48 b9 00 00 00 00 00 fc ff df 48 c1 e8 03 <80> 3c 08 00 0f 85 d6 08 00 00 48 8b 5d 00 31 ff 81 e3 ff 0f 00 00 RSP: 0018:ffffc90002a2fca8 EFLAGS: 00010206 RAX: 0000000000000003 RBX: dffffc0000000000 RCX: dffffc0000000000 RDX: ffff8881074a4980 RSI: ffffffff85809cef RDI: 0000000000000005 RBP: 0000000000000018 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000080000000 R11: ffffffff8a80008b R12: 0000000000000000 R13: 0000000000004000 R14: ffff8880162ec380 R15: 0000000080000000 FS: 0000555556e1b3c0(0000) GS:ffff888063a00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020000000 CR3: 000000001b7ab000 CR4: 0000000000750ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 ---------------- Code disassembly (best guess): 0: 83 c5 18 add $0x18,%ebp 3: 44 89 e7 mov %r12d,%edi 6: e8 cf 73 04 fc call 0xfc0473da b: 45 39 fc cmp %r15d,%r12d e: 0f 84 fe 00 00 00 je 0x112 14: e8 21 78 04 fc call 0xfc04783a 19: 48 89 e8 mov %rbp,%rax 1c: 48 b9 00 00 00 00 00 movabs $0xdffffc0000000000,%rcx 23: fc ff df 26: 48 c1 e8 03 shr $0x3,%rax * 2a: 80 3c 08 00 cmpb $0x0,(%rax,%rcx,1) <-- trapping instruction 2e: 0f 85 d6 08 00 00 jne 0x90a 34: 48 8b 5d 00 mov 0x0(%rbp),%rbx 38: 31 ff xor %edi,%edi 3a: 81 e3 ff 0f 00 00 and $0xfff,%ebx ``` We analyzed the root cause of this bug. In function udmabuf_ioctl_create_list, line 321, if list_limit is lower than 0, list_limit will be converted to uint before comparison. This would cause head.count to be an arbitrary large number, and the lsize therefore will become 0 because of overflow, causing the return value of memdup_user changed to 0x10. One possible fix could be change list_limit from int type to uint, since the limit should never be below 0. If you have any questions, please contact us. Reported by: Yue Sun <samsun1006219@xxxxxxxxx> Reported by: xingwei lee <xrivendell7@xxxxxxxxx> Best Regards, Yue
