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Message-ID: <2024062007-CVE-2021-47618-fd65@gregkh>
Date: Thu, 20 Jun 2024 12:57:07 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.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 35aa1df43283 and fixed in 5.15.19 with commit 1515e72aae80
Issue introduced in 2.6.25 with commit 35aa1df43283 and fixed in 5.16.5 with commit ba1863be105b
Issue introduced in 2.6.25 with commit 35aa1df43283 and fixed in 5.17 with commit 8b59b0a53c84
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
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