| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2021-47618: ARM: 9170/1: fix panic when kasan and kprobe are enabled |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| ARM: 9170/1: fix panic when kasan and kprobe are enabled |
| |
| arm32 uses software to simulate the instruction replaced |
| by kprobe. some instructions may be simulated by constructing |
| assembly functions. therefore, before executing instruction |
| simulation, it is necessary to construct assembly function |
| execution environment in C language through binding registers. |
| after kasan is enabled, the register binding relationship will |
| be destroyed, resulting in instruction simulation errors and |
| causing kernel panic. |
| |
| the kprobe emulate instruction function is distributed in three |
| files: actions-common.c actions-arm.c actions-thumb.c, so disable |
| KASAN when compiling these files. |
| |
| for example, use kprobe insert on cap_capable+20 after kasan |
| enabled, the cap_capable assembly code is as follows: |
| <cap_capable>: |
| e92d47f0 push {r4, r5, r6, r7, r8, r9, sl, lr} |
| e1a05000 mov r5, r0 |
| e280006c add r0, r0, #108 ; 0x6c |
| e1a04001 mov r4, r1 |
| e1a06002 mov r6, r2 |
| e59fa090 ldr sl, [pc, #144] ; |
| ebfc7bf8 bl c03aa4b4 <__asan_load4> |
| e595706c ldr r7, [r5, #108] ; 0x6c |
| e2859014 add r9, r5, #20 |
| ...... |
| The emulate_ldr assembly code after enabling kasan is as follows: |
| c06f1384 <emulate_ldr>: |
| e92d47f0 push {r4, r5, r6, r7, r8, r9, sl, lr} |
| e282803c add r8, r2, #60 ; 0x3c |
| e1a05000 mov r5, r0 |
| e7e37855 ubfx r7, r5, #16, #4 |
| e1a00008 mov r0, r8 |
| e1a09001 mov r9, r1 |
| e1a04002 mov r4, r2 |
| ebf35462 bl c03c6530 <__asan_load4> |
| e357000f cmp r7, #15 |
| e7e36655 ubfx r6, r5, #12, #4 |
| e205a00f and sl, r5, #15 |
| 0a000001 beq c06f13bc <emulate_ldr+0x38> |
| e0840107 add r0, r4, r7, lsl #2 |
| ebf3545c bl c03c6530 <__asan_load4> |
| e084010a add r0, r4, sl, lsl #2 |
| ebf3545a bl c03c6530 <__asan_load4> |
| e2890010 add r0, r9, #16 |
| ebf35458 bl c03c6530 <__asan_load4> |
| e5990010 ldr r0, [r9, #16] |
| e12fff30 blx r0 |
| e356000f cm r6, #15 |
| 1a000014 bne c06f1430 <emulate_ldr+0xac> |
| e1a06000 mov r6, r0 |
| e2840040 add r0, r4, #64 ; 0x40 |
| ...... |
| |
| when running in emulate_ldr to simulate the ldr instruction, panic |
| occurred, and the log is as follows: |
| Unable to handle kernel NULL pointer dereference at virtual address |
| 00000090 |
| pgd = ecb46400 |
| [00000090] *pgd=2e0fa003, *pmd=00000000 |
| Internal error: Oops: 206 [#1] SMP ARM |
| PC is at cap_capable+0x14/0xb0 |
| LR is at emulate_ldr+0x50/0xc0 |
| psr: 600d0293 sp : ecd63af8 ip : 00000004 fp : c0a7c30c |
| r10: 00000000 r9 : c30897f4 r8 : ecd63cd4 |
| r7 : 0000000f r6 : 0000000a r5 : e59fa090 r4 : ecd63c98 |
| r3 : c06ae294 r2 : 00000000 r1 : b7611300 r0 : bf4ec008 |
| Flags: nZCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment user |
| Control: 32c5387d Table: 2d546400 DAC: 55555555 |
| Process bash (pid: 1643, stack limit = 0xecd60190) |
| (cap_capable) from (kprobe_handler+0x218/0x340) |
| (kprobe_handler) from (kprobe_trap_handler+0x24/0x48) |
| (kprobe_trap_handler) from (do_undefinstr+0x13c/0x364) |
| (do_undefinstr) from (__und_svc_finish+0x0/0x30) |
| (__und_svc_finish) from (cap_capable+0x18/0xb0) |
| (cap_capable) from (cap_vm_enough_memory+0x38/0x48) |
| (cap_vm_enough_memory) from |
| (security_vm_enough_memory_mm+0x48/0x6c) |
| (security_vm_enough_memory_mm) from |
| (copy_process.constprop.5+0x16b4/0x25c8) |
| (copy_process.constprop.5) from (_do_fork+0xe8/0x55c) |
| (_do_fork) from (SyS_clone+0x1c/0x24) |
| (SyS_clone) from (__sys_trace_return+0x0/0x10) |
| Code: 0050a0e1 6c0080e2 0140a0e1 0260a0e1 (f801f0e7) |
| |
| The Linux kernel CVE team has assigned CVE-2021-47618 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 2.6.25 with commit 35aa1df4328340f38edc46f00837f08d33d49f63 and fixed in 5.15.19 with commit 1515e72aae803fc6b466adf918e71c4e4c9d5b3d |
| Issue introduced in 2.6.25 with commit 35aa1df4328340f38edc46f00837f08d33d49f63 and fixed in 5.16.5 with commit ba1863be105b06e10d0e2f6b1b8a0570801cfc71 |
| Issue introduced in 2.6.25 with commit 35aa1df4328340f38edc46f00837f08d33d49f63 and fixed in 5.17 with commit 8b59b0a53c840921b625378f137e88adfa87647e |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2021-47618 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| arch/arm/probes/kprobes/Makefile |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/1515e72aae803fc6b466adf918e71c4e4c9d5b3d |
| https://git.kernel.org/stable/c/ba1863be105b06e10d0e2f6b1b8a0570801cfc71 |
| https://git.kernel.org/stable/c/8b59b0a53c840921b625378f137e88adfa87647e |
