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x86/fault: Fix wrong signal when vsyscall fails with pkey

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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/202109202245.APvuT8BX-lkp@intel.com ]

Fixes: 5042d40a26 ("x86/fault: Bypass no_context() for implicit kernel faults from usermode")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Jiashuo Liang <liangjs@pku.edu.cn>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/20210730030152.249106-1-liangjs@pku.edu.cn
This commit is contained in:
Jiashuo Liang 2021-07-30 11:01:52 +08:00 committed by Borislav Petkov
parent e4e737bb5c
commit d4ffd5df9d
3 changed files with 20 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/include/asm/pkeys.h
View File

@ -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

26
arch/x86/mm/fault.c
View File

@ -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;
}

2
include/linux/pkeys.h
View File

@ -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 */