cve/published/2022/CVE-2022-49888.mbox - pub/scm/linux/security/vulns - Git at Google

 From bippy-1.1.0 Mon Sep 17 00:00:00 2001
 From: Greg Kroah-Hartman <gregkh@kernel.org>
 To: <linux-cve-announce@vger.kernel.org>
 Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org>
 Subject: CVE-2022-49888: arm64: entry: avoid kprobe recursion

 Description
 ===========

 In the Linux kernel, the following vulnerability has been resolved:

 arm64: entry: avoid kprobe recursion

 The cortex_a76_erratum_1463225_debug_handler() function is called when
 handling debug exceptions (and synchronous exceptions from BRK
 instructions), and so is called when a probed function executes. If the
 compiler does not inline cortex_a76_erratum_1463225_debug_handler(), it
 can be probed.

 If cortex_a76_erratum_1463225_debug_handler() is probed, any debug
 exception or software breakpoint exception will result in recursive
 exceptions leading to a stack overflow. This can be triggered with the
 ftrace multiple_probes selftest, and as per the example splat below.

 This is a regression caused by commit:

   6459b8469753e9fe ("arm64: entry: consolidate Cortex-A76 erratum 1463225 workaround")

 ... which removed the NOKPROBE_SYMBOL() annotation associated with the
 function.

 My intent was that cortex_a76_erratum_1463225_debug_handler() would be
 inlined into its caller, el1_dbg(), which is marked noinstr and cannot
 be probed. Mark cortex_a76_erratum_1463225_debug_handler() as
 __always_inline to ensure this.

 Example splat prior to this patch (with recursive entries elided):

 | # echo p cortex_a76_erratum_1463225_debug_handler > /sys/kernel/debug/tracing/kprobe_events
 | # echo p do_el0_svc >> /sys/kernel/debug/tracing/kprobe_events
 | # echo 1 > /sys/kernel/debug/tracing/events/kprobes/enable
 | Insufficient stack space to handle exception!
 | ESR: 0x0000000096000047 -- DABT (current EL)
 | FAR: 0xffff800009cefff0
 | Task stack:     [0xffff800009cf0000..0xffff800009cf4000]
 | IRQ stack:      [0xffff800008000000..0xffff800008004000]
 | Overflow stack: [0xffff00007fbc00f0..0xffff00007fbc10f0]
 | CPU: 0 PID: 145 Comm: sh Not tainted 6.0.0 #2
 | Hardware name: linux,dummy-virt (DT)
 | pstate: 604003c5 (nZCv DAIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
 | pc : arm64_enter_el1_dbg+0x4/0x20
 | lr : el1_dbg+0x24/0x5c
 | sp : ffff800009cf0000
 | x29: ffff800009cf0000 x28: ffff000002c74740 x27: 0000000000000000
 | x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000
 | x23: 00000000604003c5 x22: ffff80000801745c x21: 0000aaaac95ac068
 | x20: 00000000f2000004 x19: ffff800009cf0040 x18: 0000000000000000
 | x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
 | x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
 | x11: 0000000000000010 x10: ffff800008c87190 x9 : ffff800008ca00d0
 | x8 : 000000000000003c x7 : 0000000000000000 x6 : 0000000000000000
 | x5 : 0000000000000000 x4 : 0000000000000000 x3 : 00000000000043a4
 | x2 : 00000000f2000004 x1 : 00000000f2000004 x0 : ffff800009cf0040
 | Kernel panic - not syncing: kernel stack overflow
 | CPU: 0 PID: 145 Comm: sh Not tainted 6.0.0 #2
 | Hardware name: linux,dummy-virt (DT)
 | Call trace:
 |  dump_backtrace+0xe4/0x104
 |  show_stack+0x18/0x4c
 |  dump_stack_lvl+0x64/0x7c
 |  dump_stack+0x18/0x38
 |  panic+0x14c/0x338
 |  test_taint+0x0/0x2c
 |  panic_bad_stack+0x104/0x118
 |  handle_bad_stack+0x34/0x48
 |  __bad_stack+0x78/0x7c
 |  arm64_enter_el1_dbg+0x4/0x20
 |  el1h_64_sync_handler+0x40/0x98
 |  el1h_64_sync+0x64/0x68
 |  cortex_a76_erratum_1463225_debug_handler+0x0/0x34
 ...
 |  el1h_64_sync_handler+0x40/0x98
 |  el1h_64_sync+0x64/0x68
 |  cortex_a76_erratum_1463225_debug_handler+0x0/0x34
 ...
 |  el1h_64_sync_handler+0x40/0x98
 |  el1h_64_sync+0x64/0x68
 |  cortex_a76_erratum_1463225_debug_handler+0x0/0x34
 |  el1h_64_sync_handler+0x40/0x98
 |  el1h_64_sync+0x64/0x68
 |  do_el0_svc+0x0/0x28
 |  el0t_64_sync_handler+0x84/0xf0
 |  el0t_64_sync+0x18c/0x190
 | Kernel Offset: disabled
 | CPU features: 0x0080,00005021,19001080
 | Memory Limit: none
 | ---[ end Kernel panic - not syncing: kernel stack overflow ]---

 With this patch, cortex_a76_erratum_1463225_debug_handler() is inlined
 into el1_dbg(), and el1_dbg() cannot be probed:

 | # echo p cortex_a76_erratum_1463225_debug_handler > /sys/kernel/debug/tracing/kprobe_events
 | sh: write error: No such file or directory
 | # grep -w cortex_a76_erratum_1463225_debug_handler /proc/kallsyms | wc -l
 | 0
 | # echo p el1_dbg > /sys/kernel/debug/tracing/kprobe_events
 | sh: write error: Invalid argument
 | # grep -w el1_dbg /proc/kallsyms | wc -l
 | 1

 The Linux kernel CVE team has assigned CVE-2022-49888 to this issue.


 Affected and fixed versions
 ===========================

 	Issue introduced in 5.12 with commit 6459b8469753e9feaa8b34691d097cffad905931 and fixed in 5.15.78 with commit 71d6c33fe223255f4416a01514da2c0bc3e283e7
 	Issue introduced in 5.12 with commit 6459b8469753e9feaa8b34691d097cffad905931 and fixed in 6.0.8 with commit db66629d43b2d12cb43b004a4ca6be1d03228e97
 	Issue introduced in 5.12 with commit 6459b8469753e9feaa8b34691d097cffad905931 and fixed in 6.1 with commit 024f4b2e1f874934943eb2d3d288ebc52c79f55c

 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-2022-49888
 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/arm64/kernel/entry-common.c


 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/71d6c33fe223255f4416a01514da2c0bc3e283e7
 	https://git.kernel.org/stable/c/db66629d43b2d12cb43b004a4ca6be1d03228e97
 	https://git.kernel.org/stable/c/024f4b2e1f874934943eb2d3d288ebc52c79f55c
	From bippy-1.1.0 Mon Sep 17 00:00:00 2001
	From: Greg Kroah-Hartman <gregkh@kernel.org>
	To: <linux-cve-announce@vger.kernel.org>
	Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org>
	Subject: CVE-2022-49888: arm64: entry: avoid kprobe recursion

	Description
	===========

	In the Linux kernel, the following vulnerability has been resolved:

	arm64: entry: avoid kprobe recursion

	The cortex_a76_erratum_1463225_debug_handler() function is called when
	handling debug exceptions (and synchronous exceptions from BRK
	instructions), and so is called when a probed function executes. If the
	compiler does not inline cortex_a76_erratum_1463225_debug_handler(), it
	can be probed.

	If cortex_a76_erratum_1463225_debug_handler() is probed, any debug
	exception or software breakpoint exception will result in recursive
	exceptions leading to a stack overflow. This can be triggered with the
	ftrace multiple_probes selftest, and as per the example splat below.

	This is a regression caused by commit:

	6459b8469753e9fe ("arm64: entry: consolidate Cortex-A76 erratum 1463225 workaround")

	... which removed the NOKPROBE_SYMBOL() annotation associated with the
	function.

	My intent was that cortex_a76_erratum_1463225_debug_handler() would be
	inlined into its caller, el1_dbg(), which is marked noinstr and cannot
	be probed. Mark cortex_a76_erratum_1463225_debug_handler() as
	__always_inline to ensure this.

	Example splat prior to this patch (with recursive entries elided):

	\| # echo p cortex_a76_erratum_1463225_debug_handler > /sys/kernel/debug/tracing/kprobe_events
	\| # echo p do_el0_svc >> /sys/kernel/debug/tracing/kprobe_events
	\| # echo 1 > /sys/kernel/debug/tracing/events/kprobes/enable
	\| Insufficient stack space to handle exception!
	\| ESR: 0x0000000096000047 -- DABT (current EL)
	\| FAR: 0xffff800009cefff0
	\| Task stack: [0xffff800009cf0000..0xffff800009cf4000]
	\| IRQ stack: [0xffff800008000000..0xffff800008004000]
	\| Overflow stack: [0xffff00007fbc00f0..0xffff00007fbc10f0]
	\| CPU: 0 PID: 145 Comm: sh Not tainted 6.0.0 #2
	\| Hardware name: linux,dummy-virt (DT)
	\| pstate: 604003c5 (nZCv DAIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
	\| pc : arm64_enter_el1_dbg+0x4/0x20
	\| lr : el1_dbg+0x24/0x5c
	\| sp : ffff800009cf0000
	\| x29: ffff800009cf0000 x28: ffff000002c74740 x27: 0000000000000000
	\| x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000
	\| x23: 00000000604003c5 x22: ffff80000801745c x21: 0000aaaac95ac068
	\| x20: 00000000f2000004 x19: ffff800009cf0040 x18: 0000000000000000
	\| x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
	\| x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
	\| x11: 0000000000000010 x10: ffff800008c87190 x9 : ffff800008ca00d0
	\| x8 : 000000000000003c x7 : 0000000000000000 x6 : 0000000000000000
	\| x5 : 0000000000000000 x4 : 0000000000000000 x3 : 00000000000043a4
	\| x2 : 00000000f2000004 x1 : 00000000f2000004 x0 : ffff800009cf0040
	\| Kernel panic - not syncing: kernel stack overflow
	\| CPU: 0 PID: 145 Comm: sh Not tainted 6.0.0 #2
	\| Hardware name: linux,dummy-virt (DT)
	\| Call trace:
	\| dump_backtrace+0xe4/0x104
	\| show_stack+0x18/0x4c
	\| dump_stack_lvl+0x64/0x7c
	\| dump_stack+0x18/0x38
	\| panic+0x14c/0x338
	\| test_taint+0x0/0x2c
	\| panic_bad_stack+0x104/0x118
	\| handle_bad_stack+0x34/0x48
	\| __bad_stack+0x78/0x7c
	\| arm64_enter_el1_dbg+0x4/0x20
	\| el1h_64_sync_handler+0x40/0x98
	\| el1h_64_sync+0x64/0x68
	\| cortex_a76_erratum_1463225_debug_handler+0x0/0x34
	...
	\| el1h_64_sync_handler+0x40/0x98
	\| el1h_64_sync+0x64/0x68
	\| cortex_a76_erratum_1463225_debug_handler+0x0/0x34
	...
	\| el1h_64_sync_handler+0x40/0x98
	\| el1h_64_sync+0x64/0x68
	\| cortex_a76_erratum_1463225_debug_handler+0x0/0x34
	\| el1h_64_sync_handler+0x40/0x98
	\| el1h_64_sync+0x64/0x68
	\| do_el0_svc+0x0/0x28
	\| el0t_64_sync_handler+0x84/0xf0
	\| el0t_64_sync+0x18c/0x190
	\| Kernel Offset: disabled
	\| CPU features: 0x0080,00005021,19001080
	\| Memory Limit: none
	\| ---[ end Kernel panic - not syncing: kernel stack overflow ]---

	With this patch, cortex_a76_erratum_1463225_debug_handler() is inlined
	into el1_dbg(), and el1_dbg() cannot be probed:

	\| # echo p cortex_a76_erratum_1463225_debug_handler > /sys/kernel/debug/tracing/kprobe_events
	\| sh: write error: No such file or directory
	\| # grep -w cortex_a76_erratum_1463225_debug_handler /proc/kallsyms \| wc -l
	\| 0
	\| # echo p el1_dbg > /sys/kernel/debug/tracing/kprobe_events
	\| sh: write error: Invalid argument
	\| # grep -w el1_dbg /proc/kallsyms \| wc -l
	\| 1

	The Linux kernel CVE team has assigned CVE-2022-49888 to this issue.


	Affected and fixed versions
	===========================

	Issue introduced in 5.12 with commit 6459b8469753e9feaa8b34691d097cffad905931 and fixed in 5.15.78 with commit 71d6c33fe223255f4416a01514da2c0bc3e283e7
	Issue introduced in 5.12 with commit 6459b8469753e9feaa8b34691d097cffad905931 and fixed in 6.0.8 with commit db66629d43b2d12cb43b004a4ca6be1d03228e97
	Issue introduced in 5.12 with commit 6459b8469753e9feaa8b34691d097cffad905931 and fixed in 6.1 with commit 024f4b2e1f874934943eb2d3d288ebc52c79f55c

	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-2022-49888
	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/arm64/kernel/entry-common.c


	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/71d6c33fe223255f4416a01514da2c0bc3e283e7
	https://git.kernel.org/stable/c/db66629d43b2d12cb43b004a4ca6be1d03228e97
	https://git.kernel.org/stable/c/024f4b2e1f874934943eb2d3d288ebc52c79f55c