The function __bad_area_nosemaphore() calls kernelmode_fixup_or_oops() with
parameter "signal" being "pkey", which will send a signal numbered "pkey".
This bug appears when the kernel fail to access user-given memory pages
that are protected by pkey, so it can go through the do_user_addr_fault()
path and pass the !user_mode() check in __bad_area_nosemaphore(). Most
cases will simply run the kernel fixup code to make an -EFAULT. But when
another condition current->thread.sig_on_uaccess_err is met, which is
only used to emulate vsyscall, we will generate the wrong signal.
A new parameter "pkey" is added to kernelmode_fixup_or_oops() to fix it.
Fixes: 5042d40a264c ("x86/fault: Bypass no_context() for implicit kernel faults from usermode")
Signed-off-by: Jiashuo Liang <[email protected]>
---
Changes in v2:
- Use ARCH_DEFAULT_PKEY instead of 0 for unused pkey parameter.
arch/x86/mm/fault.c | 26 ++++++++++++++++++--------
1 file changed, 18 insertions(+), 8 deletions(-)
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index b2eefdefc108..84a2c8c4af73 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -710,7 +710,8 @@ page_fault_oops(struct pt_regs *regs, unsigned long error_code,
static noinline void
kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code,
- unsigned long address, int signal, int si_code)
+ unsigned long address, int signal, int si_code,
+ u32 pkey)
{
WARN_ON_ONCE(user_mode(regs));
@@ -735,8 +736,12 @@ kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code,
set_signal_archinfo(address, error_code);
- /* XXX: hwpoison faults will set the wrong code. */
- force_sig_fault(signal, si_code, (void __user *)address);
+ if (si_code == SEGV_PKUERR) {
+ force_sig_pkuerr((void __user *)address, pkey);
+ } else {
+ /* XXX: hwpoison faults will set the wrong code. */
+ force_sig_fault(signal, si_code, (void __user *)address);
+ }
}
/*
@@ -798,7 +803,8 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
struct task_struct *tsk = current;
if (!user_mode(regs)) {
- kernelmode_fixup_or_oops(regs, error_code, address, pkey, si_code);
+ kernelmode_fixup_or_oops(regs, error_code, address,
+ SIGSEGV, si_code, pkey);
return;
}
@@ -930,7 +936,8 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
{
/* Kernel mode? Handle exceptions or die: */
if (!user_mode(regs)) {
- kernelmode_fixup_or_oops(regs, error_code, address, SIGBUS, BUS_ADRERR);
+ kernelmode_fixup_or_oops(regs, error_code, address,
+ SIGBUS, BUS_ADRERR, ARCH_DEFAULT_PKEY);
return;
}
@@ -1396,7 +1403,8 @@ void do_user_addr_fault(struct pt_regs *regs,
*/
if (!user_mode(regs))
kernelmode_fixup_or_oops(regs, error_code, address,
- SIGBUS, BUS_ADRERR);
+ SIGBUS, BUS_ADRERR,
+ ARCH_DEFAULT_PKEY);
return;
}
@@ -1416,7 +1424,8 @@ void do_user_addr_fault(struct pt_regs *regs,
return;
if (fatal_signal_pending(current) && !user_mode(regs)) {
- kernelmode_fixup_or_oops(regs, error_code, address, 0, 0);
+ kernelmode_fixup_or_oops(regs, error_code, address,
+ 0, 0, ARCH_DEFAULT_PKEY);
return;
}
@@ -1424,7 +1433,8 @@ void do_user_addr_fault(struct pt_regs *regs,
/* Kernel mode? Handle exceptions or die: */
if (!user_mode(regs)) {
kernelmode_fixup_or_oops(regs, error_code, address,
- SIGSEGV, SEGV_MAPERR);
+ SIGSEGV, SEGV_MAPERR,
+ ARCH_DEFAULT_PKEY);
return;
}
--
2.32.0
On 7/29/21 8:01 PM, Jiashuo Liang wrote:
> The function __bad_area_nosemaphore() calls kernelmode_fixup_or_oops() with
> parameter "signal" being "pkey", which will send a signal numbered "pkey".
>
> This bug appears when the kernel fail to access user-given memory pages
> that are protected by pkey, so it can go through the do_user_addr_fault()
> path and pass the !user_mode() check in __bad_area_nosemaphore(). Most
> cases will simply run the kernel fixup code to make an -EFAULT. But when
> another condition current->thread.sig_on_uaccess_err is met, which is
> only used to emulate vsyscall, we will generate the wrong signal.
>
> A new parameter "pkey" is added to kernelmode_fixup_or_oops() to fix it.
>
> Fixes: 5042d40a264c ("x86/fault: Bypass no_context() for implicit kernel faults from usermode")
> Signed-off-by: Jiashuo Liang <[email protected]>
This is pretty obscure, only affecting vsyscall emulation, but:
Acked-by: Dave Hansen <[email protected]>
On Mon, 2021-08-23 at 07:55 -0700, Dave Hansen wrote:
> On 7/29/21 8:01 PM, Jiashuo Liang wrote:
>> The function __bad_area_nosemaphore() calls kernelmode_fixup_or_oops() with
>> parameter "signal" being "pkey", which will send a signal numbered "pkey".
>>
>> This bug appears when the kernel fail to access user-given memory pages
>> that are protected by pkey, so it can go through the do_user_addr_fault()
>> path and pass the !user_mode() check in __bad_area_nosemaphore(). Most
>> cases will simply run the kernel fixup code to make an -EFAULT. But when
>> another condition current->thread.sig_on_uaccess_err is met, which is
>> only used to emulate vsyscall, we will generate the wrong signal.
>>
>> A new parameter "pkey" is added to kernelmode_fixup_or_oops() to fix it.
>>
>> Fixes: 5042d40a264c ("x86/fault: Bypass no_context() for implicit kernel faults from usermode")
>> Signed-off-by: Jiashuo Liang <[email protected]>
>
> This is pretty obscure, only affecting vsyscall emulation, but:
>
> Acked-by: Dave Hansen <[email protected]>
Ping... Is there anyone reviewing/committing this patch?
Thanks!
The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: 0829d0b6bf0fb3453608798442deaf00c4a1abec
Gitweb: https://git.kernel.org/tip/0829d0b6bf0fb3453608798442deaf00c4a1abec
Author: Jiashuo Liang <[email protected]>
AuthorDate: Fri, 30 Jul 2021 11:01:52 +08:00
Committer: Borislav Petkov <[email protected]>
CommitterDate: Mon, 20 Sep 2021 12:31:06 +02:00
x86/fault: Fix wrong signal when vsyscall fails with pkey
The function __bad_area_nosemaphore() calls kernelmode_fixup_or_oops()
with the parameter @signal being actually @pkey, which will send a
signal numbered with the argument in @pkey.
This bug can be triggered when the kernel fails to access user-given
memory pages that are protected by a pkey, so it can go down the
do_user_addr_fault() path and pass the !user_mode() check in
__bad_area_nosemaphore().
Most cases will simply run the kernel fixup code to make an -EFAULT. But
when another condition current->thread.sig_on_uaccess_err is met, which
is only used to emulate vsyscall, the kernel will generate the wrong
signal.
Add a new parameter @pkey to kernelmode_fixup_or_oops() to fix this.
[ bp: Massage commit message. ]
Fixes: 5042d40a264c ("x86/fault: Bypass no_context() for implicit kernel faults from usermode")
Signed-off-by: Jiashuo Liang <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Acked-by: Dave Hansen <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
---
arch/x86/mm/fault.c | 26 ++++++++++++++++++--------
1 file changed, 18 insertions(+), 8 deletions(-)
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index b2eefde..84a2c8c 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -710,7 +710,8 @@ oops:
static noinline void
kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code,
- unsigned long address, int signal, int si_code)
+ unsigned long address, int signal, int si_code,
+ u32 pkey)
{
WARN_ON_ONCE(user_mode(regs));
@@ -735,8 +736,12 @@ kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code,
set_signal_archinfo(address, error_code);
- /* XXX: hwpoison faults will set the wrong code. */
- force_sig_fault(signal, si_code, (void __user *)address);
+ if (si_code == SEGV_PKUERR) {
+ force_sig_pkuerr((void __user *)address, pkey);
+ } else {
+ /* XXX: hwpoison faults will set the wrong code. */
+ force_sig_fault(signal, si_code, (void __user *)address);
+ }
}
/*
@@ -798,7 +803,8 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
struct task_struct *tsk = current;
if (!user_mode(regs)) {
- kernelmode_fixup_or_oops(regs, error_code, address, pkey, si_code);
+ kernelmode_fixup_or_oops(regs, error_code, address,
+ SIGSEGV, si_code, pkey);
return;
}
@@ -930,7 +936,8 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
{
/* Kernel mode? Handle exceptions or die: */
if (!user_mode(regs)) {
- kernelmode_fixup_or_oops(regs, error_code, address, SIGBUS, BUS_ADRERR);
+ kernelmode_fixup_or_oops(regs, error_code, address,
+ SIGBUS, BUS_ADRERR, ARCH_DEFAULT_PKEY);
return;
}
@@ -1396,7 +1403,8 @@ good_area:
*/
if (!user_mode(regs))
kernelmode_fixup_or_oops(regs, error_code, address,
- SIGBUS, BUS_ADRERR);
+ SIGBUS, BUS_ADRERR,
+ ARCH_DEFAULT_PKEY);
return;
}
@@ -1416,7 +1424,8 @@ good_area:
return;
if (fatal_signal_pending(current) && !user_mode(regs)) {
- kernelmode_fixup_or_oops(regs, error_code, address, 0, 0);
+ kernelmode_fixup_or_oops(regs, error_code, address,
+ 0, 0, ARCH_DEFAULT_PKEY);
return;
}
@@ -1424,7 +1433,8 @@ good_area:
/* Kernel mode? Handle exceptions or die: */
if (!user_mode(regs)) {
kernelmode_fixup_or_oops(regs, error_code, address,
- SIGSEGV, SEGV_MAPERR);
+ SIGSEGV, SEGV_MAPERR,
+ ARCH_DEFAULT_PKEY);
return;
}
On Mon, Sep 20, 2021 at 10:42:39AM -0000, tip-bot2 for Jiashuo Liang wrote:
> The following commit has been merged into the x86/urgent branch of tip:
>
> Commit-ID: 0829d0b6bf0fb3453608798442deaf00c4a1abec
> Gitweb: https://git.kernel.org/tip/0829d0b6bf0fb3453608798442deaf00c4a1abec
> Author: Jiashuo Liang <[email protected]>
> AuthorDate: Fri, 30 Jul 2021 11:01:52 +08:00
> Committer: Borislav Petkov <[email protected]>
> CommitterDate: Mon, 20 Sep 2021 12:31:06 +02:00
>
> x86/fault: Fix wrong signal when vsyscall fails with pkey
>
> The function __bad_area_nosemaphore() calls kernelmode_fixup_or_oops()
> with the parameter @signal being actually @pkey, which will send a
> signal numbered with the argument in @pkey.
>
> This bug can be triggered when the kernel fails to access user-given
> memory pages that are protected by a pkey, so it can go down the
> do_user_addr_fault() path and pass the !user_mode() check in
> __bad_area_nosemaphore().
>
> Most cases will simply run the kernel fixup code to make an -EFAULT. But
> when another condition current->thread.sig_on_uaccess_err is met, which
> is only used to emulate vsyscall, the kernel will generate the wrong
> signal.
>
> Add a new parameter @pkey to kernelmode_fixup_or_oops() to fix this.
>
> [ bp: Massage commit message. ]
>
> Fixes: 5042d40a264c ("x86/fault: Bypass no_context() for implicit kernel faults from usermode")
> Signed-off-by: Jiashuo Liang <[email protected]>
> Signed-off-by: Borislav Petkov <[email protected]>
> Acked-by: Dave Hansen <[email protected]>
> Link: https://lkml.kernel.org/r/[email protected]
> ---
> arch/x86/mm/fault.c | 26 ++++++++++++++++++--------
> 1 file changed, 18 insertions(+), 8 deletions(-)
Zapping it again because the 0day bot found some randconfig which fails:
https://lkml.kernel.org/r/[email protected]
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: d4ffd5df9d18031b6a53f934388726775b4452d3
Gitweb: https://git.kernel.org/tip/d4ffd5df9d18031b6a53f934388726775b4452d3
Author: Jiashuo Liang <[email protected]>
AuthorDate: Fri, 30 Jul 2021 11:01:52 +08:00
Committer: Borislav Petkov <[email protected]>
CommitterDate: Mon, 20 Sep 2021 22:28:47 +02:00
x86/fault: Fix wrong signal when vsyscall fails with pkey
The function __bad_area_nosemaphore() calls kernelmode_fixup_or_oops()
with the parameter @signal being actually @pkey, which will send a
signal numbered with the argument in @pkey.
This bug can be triggered when the kernel fails to access user-given
memory pages that are protected by a pkey, so it can go down the
do_user_addr_fault() path and pass the !user_mode() check in
__bad_area_nosemaphore().
Most cases will simply run the kernel fixup code to make an -EFAULT. But
when another condition current->thread.sig_on_uaccess_err is met, which
is only used to emulate vsyscall, the kernel will generate the wrong
signal.
Add a new parameter @pkey to kernelmode_fixup_or_oops() to fix this.
[ bp: Massage commit message, fix build error as reported by the 0day
bot: https://lkml.kernel.org/r/[email protected] ]
Fixes: 5042d40a264c ("x86/fault: Bypass no_context() for implicit kernel faults from usermode")
Reported-by: kernel test robot <[email protected]>
Signed-off-by: Jiashuo Liang <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Acked-by: Dave Hansen <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
---
arch/x86/include/asm/pkeys.h | 2 --
arch/x86/mm/fault.c | 26 ++++++++++++++++++--------
include/linux/pkeys.h | 2 ++
3 files changed, 20 insertions(+), 10 deletions(-)
diff --git a/arch/x86/include/asm/pkeys.h b/arch/x86/include/asm/pkeys.h
index 5c7bcaa..1d5f14a 100644
--- a/arch/x86/include/asm/pkeys.h
+++ b/arch/x86/include/asm/pkeys.h
@@ -2,8 +2,6 @@
#ifndef _ASM_X86_PKEYS_H
#define _ASM_X86_PKEYS_H
-#define ARCH_DEFAULT_PKEY 0
-
/*
* If more than 16 keys are ever supported, a thorough audit
* will be necessary to ensure that the types that store key
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index b2eefde..84a2c8c 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -710,7 +710,8 @@ oops:
static noinline void
kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code,
- unsigned long address, int signal, int si_code)
+ unsigned long address, int signal, int si_code,
+ u32 pkey)
{
WARN_ON_ONCE(user_mode(regs));
@@ -735,8 +736,12 @@ kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code,
set_signal_archinfo(address, error_code);
- /* XXX: hwpoison faults will set the wrong code. */
- force_sig_fault(signal, si_code, (void __user *)address);
+ if (si_code == SEGV_PKUERR) {
+ force_sig_pkuerr((void __user *)address, pkey);
+ } else {
+ /* XXX: hwpoison faults will set the wrong code. */
+ force_sig_fault(signal, si_code, (void __user *)address);
+ }
}
/*
@@ -798,7 +803,8 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
struct task_struct *tsk = current;
if (!user_mode(regs)) {
- kernelmode_fixup_or_oops(regs, error_code, address, pkey, si_code);
+ kernelmode_fixup_or_oops(regs, error_code, address,
+ SIGSEGV, si_code, pkey);
return;
}
@@ -930,7 +936,8 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
{
/* Kernel mode? Handle exceptions or die: */
if (!user_mode(regs)) {
- kernelmode_fixup_or_oops(regs, error_code, address, SIGBUS, BUS_ADRERR);
+ kernelmode_fixup_or_oops(regs, error_code, address,
+ SIGBUS, BUS_ADRERR, ARCH_DEFAULT_PKEY);
return;
}
@@ -1396,7 +1403,8 @@ good_area:
*/
if (!user_mode(regs))
kernelmode_fixup_or_oops(regs, error_code, address,
- SIGBUS, BUS_ADRERR);
+ SIGBUS, BUS_ADRERR,
+ ARCH_DEFAULT_PKEY);
return;
}
@@ -1416,7 +1424,8 @@ good_area:
return;
if (fatal_signal_pending(current) && !user_mode(regs)) {
- kernelmode_fixup_or_oops(regs, error_code, address, 0, 0);
+ kernelmode_fixup_or_oops(regs, error_code, address,
+ 0, 0, ARCH_DEFAULT_PKEY);
return;
}
@@ -1424,7 +1433,8 @@ good_area:
/* Kernel mode? Handle exceptions or die: */
if (!user_mode(regs)) {
kernelmode_fixup_or_oops(regs, error_code, address,
- SIGSEGV, SEGV_MAPERR);
+ SIGSEGV, SEGV_MAPERR,
+ ARCH_DEFAULT_PKEY);
return;
}
diff --git a/include/linux/pkeys.h b/include/linux/pkeys.h
index 6beb26b..86be8bf 100644
--- a/include/linux/pkeys.h
+++ b/include/linux/pkeys.h
@@ -4,6 +4,8 @@
#include <linux/mm.h>
+#define ARCH_DEFAULT_PKEY 0
+
#ifdef CONFIG_ARCH_HAS_PKEYS
#include <asm/pkeys.h>
#else /* ! CONFIG_ARCH_HAS_PKEYS */