On Fri, 23 Sep 2022 17:32:53 +0800, Li Huafei wrote:
> I found a null pointer reference in arch_prepare_kprobe():
>
> # echo 'p cmdline_proc_show' > kprobe_events
> # echo 'p cmdline_proc_show+16' >> kprobe_events
> [ 67.278533][ T122] Kernel attempted to read user page (0) - exploit
> attempt? (uid: 0)
> [ 67.279326][ T122] BUG: Kernel NULL pointer dereference on read at
> 0x00000000
> [ 67.279738][ T122] Faulting instruction address: 0xc000000000050bfc
> [ 67.280486][ T122] Oops: Kernel access of bad area, sig: 11 [#1]
> [ 67.280846][ T122] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA
> PowerNV
> [ 67.281435][ T122] Modules linked in:
> [ 67.281903][ T122] CPU: 0 PID: 122 Comm: sh Not tainted
> 6.0.0-rc3-00007-gdcf8e5633e2e #10
> [ 67.282547][ T122] NIP: c000000000050bfc LR: c000000000050bec CTR:
> 0000000000005bdc
> [ 67.282920][ T122] REGS: c0000000348475b0 TRAP: 0300 Not tainted
> (6.0.0-rc3-00007-gdcf8e5633e2e)
> [ 67.283424][ T122] MSR: 9000000000009033 <SF,HV,EE,ME,IR,DR,RI,LE>
> CR: 88002444 XER: 20040006
> [ 67.284023][ T122] CFAR: c00000000022d100 DAR: 0000000000000000 DSISR:
> 40000000 IRQMASK: 0
> [ 67.284023][ T122] GPR00: c000000000050bec c000000034847850
> c0000000013f6100 c000000001fb7718
> [ 67.284023][ T122] GPR04: c000000000515c10 c000000000e5fe08
> c00000000133da60 c000000004839300
> [ 67.284023][ T122] GPR08: c0000000014ffb98 0000000000000000
> c000000000515c0c c000000000e18576
> [ 67.284023][ T122] GPR12: c000000000e60170 c0000000015a0000
> 00000001155e0460 0000000000000000
> [ 67.284023][ T122] GPR16: 0000000000000000 00007fffe8eeb3c8
> 0000000116320728 0000000000000000
> [ 67.284023][ T122] GPR20: 0000000116320720 0000000000000000
> c0000000012fa918 0000000000000006
> [ 67.284023][ T122] GPR24: c0000000014ffb98 c0000000011ed360
> 0000000000000000 c000000001fb7928
> [ 67.284023][ T122] GPR28: 0000000000000000 0000000000000000
> 000000007c0802a6 c000000001fb7918
> [ 67.287799][ T122] NIP [c000000000050bfc]
> arch_prepare_kprobe+0x10c/0x2d0
> [ 67.288490][ T122] LR [c000000000050bec] arch_prepare_kprobe+0xfc/0x2d0
> [ 67.289025][ T122] Call Trace:
> [ 67.289268][ T122] [c000000034847850] [c0000000012f77a0]
> 0xc0000000012f77a0 (unreliable)
> [ 67.289999][ T122] [c0000000348478d0] [c000000000231320]
> register_kprobe+0x3c0/0x7a0
> [ 67.290439][ T122] [c000000034847940] [c0000000002938c0]
> __register_trace_kprobe+0x140/0x1a0
> [ 67.290898][ T122] [c0000000348479b0] [c0000000002944c4]
> __trace_kprobe_create+0x794/0x1040
> [ 67.291330][ T122] [c000000034847b60] [c0000000002a1614]
> trace_probe_create+0xc4/0xe0
> [ 67.291717][ T122] [c000000034847bb0] [c00000000029363c]
> create_or_delete_trace_kprobe+0x2c/0x80
> [ 67.292158][ T122] [c000000034847bd0] [c000000000264420]
> trace_parse_run_command+0xf0/0x210
> [ 67.292611][ T122] [c000000034847c70] [c0000000002934a0]
> probes_write+0x20/0x40
> [ 67.292996][ T122] [c000000034847c90] [c00000000045e98c]
> vfs_write+0xfc/0x450
> [ 67.293356][ T122] [c000000034847d50] [c00000000045eec4]
> ksys_write+0x84/0x140
> [ 67.293716][ T122] [c000000034847da0] [c00000000002e4fc]
> system_call_exception+0x17c/0x3a0
> [ 67.294186][ T122] [c000000034847e10] [c00000000000c0e8]
> system_call_vectored_common+0xe8/0x278
> [ 67.294680][ T122] --- interrupt: 3000 at 0x7fffa5682de0
> [ 67.294937][ T122] NIP: 00007fffa5682de0 LR: 0000000000000000 CTR:
> 0000000000000000
> [ 67.295313][ T122] REGS: c000000034847e80 TRAP: 3000 Not tainted
> (6.0.0-rc3-00007-gdcf8e5633e2e)
> [ 67.295725][ T122] MSR: 900000000280f033
> <SF,HV,VEC,VSX,EE,PR,FP,ME,IR,DR,RI,LE> CR: 44002408 XER: 00000000
> [ 67.296291][ T122] IRQMASK: 0
> [ 67.296291][ T122] GPR00: 0000000000000004 00007fffe8eeaec0
> 00007fffa5757300 0000000000000001
> [ 67.296291][ T122] GPR04: 0000000116329c60 0000000000000017
> 0000000000116329 0000000000000000
> [ 67.296291][ T122] GPR08: 0000000000000006 0000000000000000
> 0000000000000000 0000000000000000
> [ 67.296291][ T122] GPR12: 0000000000000000 00007fffa580ac60
> 00000001155e0460 0000000000000000
> [ 67.296291][ T122] GPR16: 0000000000000000 00007fffe8eeb3c8
> 0000000116320728 0000000000000000
> [ 67.296291][ T122] GPR20: 0000000116320720 0000000000000000
> 0000000000000000 0000000000000002
> [ 67.296291][ T122] GPR24: 00000001163206f0 0000000000000020
> 00007fffe8eeafa0 0000000000000001
> [ 67.296291][ T122] GPR28: 0000000000000000 0000000000000017
> 0000000116329c60 0000000000000001
> [ 67.299570][ T122] NIP [00007fffa5682de0] 0x7fffa5682de0
> [ 67.299837][ T122] LR [0000000000000000] 0x0
> [ 67.300072][ T122] --- interrupt: 3000
> [ 67.300447][ T122] Instruction dump:
> [ 67.300736][ T122] 386319d8 481342f5 60000000 60000000 60000000
> e87f0028 3863fffc 481dc4d1
> [ 67.301230][ T122] 60000000 2c230000 41820018 e9230058 <81290000>
> 552936be 2c090001 4182018c
> [ 67.302102][ T122] ---[ end trace 0000000000000000 ]---
> [ 67.302496][ T122]
>
> [...]
Applied to powerpc/next.
[1/1] powerpc/kprobes: Fix null pointer reference in arch_prepare_kprobe()
https://git.kernel.org/powerpc/c/97f88a3d723162781d6cbfdc7b9617eefab55b19
cheers
