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Subject[PATCH v3] x86/fault: Send a SIGBUS to user process always for hwpoison page access.
When one page is already hwpoisoned by MCE AO action, processes may not
be killed, processes mapping this page may make a syscall include this
page and result to trigger a VM_FAULT_HWPOISON fault, as it's in kernel
mode it may be fixed by fixup_exception, current code will just return
error code to user code.

This is not sufficient, we should send a SIGBUS to the process and log
the info to console, as we can't trust the process will handle the error
correctly.

Suggested-by: Feng Yang <yangfeng1@kingsoft.com>
Signed-off-by: Aili Yao <yaoaili@kingsoft.com>
---
arch/x86/mm/fault.c | 62 +++++++++++++++++++++++++++++----------------
1 file changed, 40 insertions(+), 22 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 08f5f74cf989..62df798abb56 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -617,6 +617,30 @@ static void set_signal_archinfo(unsigned long address,
tsk->thread.cr2 = address;
}

+static int
+do_sigbus_mceerr(unsigned long error_code, unsigned long address, vm_fault_t fault, int prepared)
+{
+ struct task_struct *tsk = current;
+ unsigned int lsb = 0;
+
+ if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
+ pr_err(
+ "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
+ tsk->comm, tsk->pid, address);
+ if (fault & VM_FAULT_HWPOISON_LARGE)
+ lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
+ if (fault & VM_FAULT_HWPOISON)
+ lsb = PAGE_SHIFT;
+ if (!prepared) {
+ sanitize_error_code(address, &error_code);
+ set_signal_archinfo(address, error_code);
+ }
+ force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
+ return 1;
+ }
+ return 0;
+}
+
static noinline void
page_fault_oops(struct pt_regs *regs, unsigned long error_code,
unsigned long address)
@@ -694,7 +718,7 @@ 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, vm_fault_t fault)
{
WARN_ON_ONCE(user_mode(regs));

@@ -714,12 +738,17 @@ kernelmode_fixup_or_oops(struct pt_regs *regs, unsigned long error_code,
* In this case we need to make sure we're not recursively
* faulting through the emulate_vsyscall() logic.
*/
+
+ /* Sending MCERR Sigbus for page fault error from hwpoison */
+ if (IS_ENABLED(CONFIG_MEMORY_FAILURE)
+ && do_sigbus_mceerr(error_code, address, fault, 0))
+ return;
+
if (current->thread.sig_on_uaccess_err && signal) {
sanitize_error_code(address, &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);
}

@@ -782,7 +811,7 @@ __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, pkey, si_code, 0);
return;
}

@@ -914,7 +943,7 @@ 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, fault);
return;
}

@@ -929,22 +958,11 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,

set_signal_archinfo(address, error_code);

-#ifdef CONFIG_MEMORY_FAILURE
- if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
- struct task_struct *tsk = current;
- unsigned lsb = 0;
-
- pr_err(
- "MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
- tsk->comm, tsk->pid, address);
- if (fault & VM_FAULT_HWPOISON_LARGE)
- lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
- if (fault & VM_FAULT_HWPOISON)
- lsb = PAGE_SHIFT;
- force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
+ /* Sending MCERR Sigbus for page fault error from hwpoison */
+ if (IS_ENABLED(CONFIG_MEMORY_FAILURE)
+ && do_sigbus_mceerr(error_code, address, fault, 1))
return;
- }
-#endif
+
force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
}

@@ -1380,7 +1398,7 @@ 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, 0);
return;
}

@@ -1400,7 +1418,7 @@ 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, 0);
return;
}

@@ -1408,7 +1426,7 @@ 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, 0);
return;
}

base-commit: 167104452673f6c1b0e7bdbdf6a4b25f862e2319
prerequisite-patch-id: 6d1e0f23558f83f851ae883633b5c498f0c826c6
prerequisite-patch-id: 2dd1d48b132e6fa0c7b564dbbd9af2e667ebc997
prerequisite-patch-id: 4fa3543c8706f54bfc0b12b787222c65ff701c10
prerequisite-patch-id: 7465d0fe35a243e23f21a60b3595c09f4a95bdc2
prerequisite-patch-id: 0e7f44bbfa3911af10aa208dee5a8f7fb33f54b7
prerequisite-patch-id: 19bdc10dd055ae8761a8a87f6912f84b4bda68be
prerequisite-patch-id: df466945a2b3150abca123da0467b52220c3cc19
prerequisite-patch-id: 6678a8efeced8907cbdf167221b7d8c0deaa6c44
prerequisite-patch-id: d2270eca0467bbd5e8575fda9f18ddf7943f5562
prerequisite-patch-id: 97ab827e60b94faa6e4fc9f955aa88c4f51ceb5a
--
2.25.1

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