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Message-Id: <5281297D-B66E-4A4C-9B41-D2242F6B7AE7@lca.pw>
Date: Tue, 24 Mar 2020 23:24:01 -0400
From: Qian Cai <cai@....pw>
To: Al Viro <viro@...iv.linux.org.uk>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: Null-ptr-deref due to "sanitized pathwalk machinery (v4)"
> On Mar 24, 2020, at 10:13 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
>
> On Tue, Mar 24, 2020 at 09:49:48PM -0400, Qian Cai wrote:
>
>> It does not catch anything at all with the patch,
>
> You mean, oops happens, but neither WARN_ON() is triggered?
> Lovely... Just to make sure: could you slap the same couple
> of lines just before
> if (unlikely(!d_can_lookup(nd->path.dentry))) {
> in link_path_walk(), just to check if I have misread the trace
> you've got?
>
> Does that (+ other two inserts) end up with
> 1) some of these WARN_ON() triggered when oops happens or
> 2) oops is happening, but neither WARN_ON() triggers or
> 3) oops not happening / becoming harder to hit?
Only the one just before
if (unlikely(!d_can_lookup(nd->path.dentry))) {
In link_path_walk() will trigger.
[ 245.766216][ T5020] WARNING: CPU: 65 PID: 5020 at fs/namei.c:2182 link_path_walk+0x29c/0x510
[ 245.766242][ T5020] Modules linked in: kvm_hv kvm ip_tables x_tables xfs sd_mod bnx2x ahci libahci mdio libata tg3 libphy firmware_class dm_mirror dm_region_hash dm_log dm_mod
[ 245.766289][ T5020] CPU: 65 PID: 5020 Comm: vdo Not tainted 5.6.0-rc7-next-20200324+ #6
[ 245.766314][ T5020] NIP: c0000000004dbffc LR: c0000000004dc0e0 CTR: 0000000000000000
[ 245.766338][ T5020] REGS: c000200ec1fcf6c0 TRAP: 0700 Not tainted (5.6.0-rc7-next-20200324+)
[ 245.766374][ T5020] MSR: 9000000000029033 <SF,HV,EE,ME,IR,DR,RI,LE> CR: 28228422 XER: 20040000
[ 245.766415][ T5020] CFAR: c0000000004dc0e4 IRQMASK: 0
[ 245.766415][ T5020] GPR00: c0000000004dc0e0 c000200ec1fcf950 c00000000165a500 0000000000000000
[ 245.766415][ T5020] GPR04: c000000001511408 0000000000000000 c000200ec1fcf6a4 0000000000000002
[ 245.766415][ T5020] GPR08: 0000000000000001 0000000000000000 0000000000000001 0000000000000001
[ 245.766415][ T5020] GPR12: 0000000000008000 c000201fff7fa700 00007fffa6f0f360 c000200579ec7ae0
[ 245.766415][ T5020] GPR16: 7fffffffffffffff fffffffffffffe00 0000000000000000 0000000000000000
[ 245.766415][ T5020] GPR20: c000000c415a2498 c0002011e2cabd83 2f2f2f2f2f2f2f2f 0000000000000003
[ 245.766415][ T5020] GPR24: 0000000000000000 c000200ec1fcfab8 fffffffffffff000 0000000000200000
[ 245.766415][ T5020] GPR28: ffffffffffffffff 61c8864680b583eb 0000000000000001 0000000000002e2e
[ 245.766632][ T5020] NIP [c0000000004dbffc] link_path_walk+0x29c/0x510
[ 245.766655][ T5020] LR [c0000000004dc0e0] link_path_walk+0x380/0x510
[ 245.766677][ T5020] Call Trace:
[ 245.766698][ T5020] [c000200ec1fcf950] [c0000000004dc0e0] link_path_walk+0x380/0x510 (unreliable)
[ 245.766725][ T5020] [c000200ec1fcfa50] [c0000000004dc3c4] path_lookupat+0x94/0x1b0
[ 245.766739][ T5020] [c000200ec1fcfa90] [c0000000004de010] filename_lookup.part.55+0xa0/0x170
[ 245.766778][ T5020] [c000200ec1fcfbd0] [c00000000096cbe8] unix_find_other+0x58/0x3c0
[ 245.766803][ T5020] [c000200ec1fcfc60] [c00000000096de54] unix_stream_connect+0x144/0x870
[ 245.766842][ T5020] [c000200ec1fcfd30] [c0000000007cf860] __sys_connect+0x140/0x170
[ 245.766881][ T5020] [c000200ec1fcfe00] [c0000000007cf8b8] sys_connect+0x28/0x40
[ 245.766897][ T5020] [c000200ec1fcfe20] [c00000000000b378] system_call+0x5c/0x68
[ 245.766921][ T5020] Instruction dump:
[ 245.766952][ T5020] 38800000 7f23cb78 7fde07b4 1d5e0030 7d295214 eaa90020 4bfffab5 2fa30000
[ 245.767003][ T5020] 409e00fc e9390008 7d2a0074 794ad182 <0b0a0000> 2fa90000 419e0184 81290000
[ 245.767031][ T5020] irq event stamp: 27044
[ 245.767052][ T5020] hardirqs last enabled at (27043): [<c0000000004db354>] handle_dots.part.47+0x224/0x960
[ 245.767068][ T5020] hardirqs last disabled at (27044): [<c000000000008fbc>] program_check_common+0x21c/0x230
[ 245.767096][ T5020] softirqs last enabled at (27018): [<c000000000968620>] unix_create1+0x1e0/0x2a0
[ 245.767144][ T5020] softirqs last disabled at (27016): [<c000000000968620>] unix_create1+0x1e0/0x2a0
[ 245.767180][ T5020] ---[ end trace 7b3382b3d92e587f ]---
[ 245.767202][ T5020] pathname = /var/run/nscd/socket
[ 245.767225][ T5020] BUG: Kernel NULL pointer dereference on read at 0x00000000
[ 245.767248][ T5020] Faulting instruction address: 0xc0000000004dc008
[ 245.767298][ T5020] Oops: Kernel access of bad area, sig: 11 [#1]
[ 245.767320][ T5020] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=256 DEBUG_PAGEALLOC NUMA PowerNV
[ 245.767354][ T5020] Modules linked in: kvm_hv kvm ip_tables x_tables xfs sd_mod bnx2x ahci libahci mdio libata tg3 libphy firmware_class dm_mirror dm_region_hash dm_log dm_mod
[ 245.767425][ T5020] CPU: 65 PID: 5020 Comm: vdo Tainted: G W 5.6.0-rc7-next-20200324+ #6
[ 245.767460][ T5020] NIP: c0000000004dc008 LR: c0000000004dc19c CTR: 0000000000000000
[ 245.767494][ T5020] REGS: c000200ec1fcf6c0 TRAP: 0300 Tainted: G W (5.6.0-rc7-next-20200324+)
[ 245.767541][ T5020] MSR: 9000000000009033 <SF,HV,EE,ME,IR,DR,RI,LE> CR: 48228222 XER: 20040000
[ 245.767579][ T5020] CFAR: c0000000004dc1a4 DAR: 0000000000000000 DSISR: 40000000 IRQMASK: 0
[ 245.767579][ T5020] GPR00: c0000000004dc19c c000200ec1fcf950 c00000000165a500 000000000000001f
[ 245.767579][ T5020] GPR04: 0000000000000006 0000000000000000 c000200ec1fcf6b4 0000000000000007
[ 245.767579][ T5020] GPR08: 0000000000000003 0000000000000000 c000200ec118aa80 0000000000000000
[ 245.767579][ T5020] GPR12: 0000000000008000 c000201fff7fa700 00007fffa6f0f360 c000200579ec7ae0
[ 245.767579][ T5020] GPR16: 7fffffffffffffff fffffffffffffe00 0000000000000000 0000000000000000
[ 245.767579][ T5020] GPR20: c000000c415a2498 c0002011e2cabd83 2f2f2f2f2f2f2f2f 0000000000000003
[ 245.767579][ T5020] GPR24: 0000000000000000 c000200ec1fcfab8 fffffffffffff000 0000000000200000
[ 245.767579][ T5020] GPR28: ffffffffffffffff 61c8864680b583eb 0000000000000001 0000000000002e2e
[ 245.767830][ T5020] NIP [c0000000004dc008] link_path_walk+0x2a8/0x510
[ 245.767852][ T5020] LR [c0000000004dc19c] link_path_walk+0x43c/0x510
[ 245.767884][ T5020] Call Trace:
[ 245.767903][ T5020] [c000200ec1fcf950] [c0000000004dc19c] link_path_walk+0x43c/0x510 (unreliable)
[ 245.767950][ T5020] [c000200ec1fcfa50] [c0000000004dc3c4] path_lookupat+0x94/0x1b0
[ 245.767974][ T5020] [c000200ec1fcfa90] [c0000000004de010] filename_lookup.part.55+0xa0/0x170
[ 245.768070][ T5020] [c000200ec1fcfbd0] [c00000000096cbe8] unix_find_other+0x58/0x3c0
[ 245.768155][ T5020] [c000200ec1fcfc60] [c00000000096de54] unix_stream_connect+0x144/0x870
[ 245.768255][ T5020] [c000200ec1fcfd30] [c0000000007cf860] __sys_connect+0x140/0x170
[ 245.768358][ T5020] [c000200ec1fcfe00] [c0000000007cf8b8] sys_connect+0x28/0x40
[ 245.768468][ T5020] [c000200ec1fcfe20] [c00000000000b378] system_call+0x5c/0x68
[ 245.768545][ T5020] Instruction dump:
[ 245.768609][ T5020] 1d5e0030 7d295214 eaa90020 4bfffab5 2fa30000 409e00fc e9390008 7d2a0074
[ 245.768705][ T5020] 794ad182 0b0a0000 2fa90000 419e0184 <81290000> 55290256 7f89d800 419efe8c
[ 245.768816][ T5020] ---[ end trace 7b3382b3d92e5880 ]---
[ 245.820494][ T5040] sda2: Can't mount, would change RO state
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