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Subject[PATCH 4.10 017/110] arm64: mm: unaligned access by user-land should be received as SIGBUS
Date
4.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Victor Kamensky <kamensky@cisco.com>

commit 09a6adf53d42ca3088fa3fb41f40b768efc711ed upstream.

After 52d7523 (arm64: mm: allow the kernel to handle alignment faults on
user accesses) commit user-land accesses that produce unaligned exceptions
like in case of aarch32 ldm/stm/ldrd/strd instructions operating on
unaligned memory received by user-land as SIGSEGV. It is wrong, it should
be reported as SIGBUS as it was before 52d7523 commit.

Changed do_bad_area function to take signal and code parameters out of esr
value using fault_info table, so in case of do_alignment_fault fault
user-land will receive SIGBUS. Wrapped access to fault_info table into
esr_to_fault_info function.

Fixes: 52d7523 (arm64: mm: allow the kernel to handle alignment faults on user accesses)
Signed-off-by: Victor Kamensky <kamensky@cisco.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/arm64/mm/fault.c | 42 ++++++++++++++++++++++++------------------
1 file changed, 24 insertions(+), 18 deletions(-)

--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -41,7 +41,20 @@
#include <asm/pgtable.h>
#include <asm/tlbflush.h>

-static const char *fault_name(unsigned int esr);
+struct fault_info {
+ int (*fn)(unsigned long addr, unsigned int esr,
+ struct pt_regs *regs);
+ int sig;
+ int code;
+ const char *name;
+};
+
+static const struct fault_info fault_info[];
+
+static inline const struct fault_info *esr_to_fault_info(unsigned int esr)
+{
+ return fault_info + (esr & 63);
+}

#ifdef CONFIG_KPROBES
static inline int notify_page_fault(struct pt_regs *regs, unsigned int esr)
@@ -196,10 +209,12 @@ static void __do_user_fault(struct task_
struct pt_regs *regs)
{
struct siginfo si;
+ const struct fault_info *inf;

if (unhandled_signal(tsk, sig) && show_unhandled_signals_ratelimited()) {
+ inf = esr_to_fault_info(esr);
pr_info("%s[%d]: unhandled %s (%d) at 0x%08lx, esr 0x%03x\n",
- tsk->comm, task_pid_nr(tsk), fault_name(esr), sig,
+ tsk->comm, task_pid_nr(tsk), inf->name, sig,
addr, esr);
show_pte(tsk->mm, addr);
show_regs(regs);
@@ -218,14 +233,16 @@ static void do_bad_area(unsigned long ad
{
struct task_struct *tsk = current;
struct mm_struct *mm = tsk->active_mm;
+ const struct fault_info *inf;

/*
* If we are in kernel mode at this point, we have no context to
* handle this fault with.
*/
- if (user_mode(regs))
- __do_user_fault(tsk, addr, esr, SIGSEGV, SEGV_MAPERR, regs);
- else
+ if (user_mode(regs)) {
+ inf = esr_to_fault_info(esr);
+ __do_user_fault(tsk, addr, esr, inf->sig, inf->code, regs);
+ } else
__do_kernel_fault(mm, addr, esr, regs);
}

@@ -487,12 +504,7 @@ static int do_bad(unsigned long addr, un
return 1;
}

-static const struct fault_info {
- int (*fn)(unsigned long addr, unsigned int esr, struct pt_regs *regs);
- int sig;
- int code;
- const char *name;
-} fault_info[] = {
+static const struct fault_info fault_info[] = {
{ do_bad, SIGBUS, 0, "ttbr address size fault" },
{ do_bad, SIGBUS, 0, "level 1 address size fault" },
{ do_bad, SIGBUS, 0, "level 2 address size fault" },
@@ -559,19 +571,13 @@ static const struct fault_info {
{ do_bad, SIGBUS, 0, "unknown 63" },
};

-static const char *fault_name(unsigned int esr)
-{
- const struct fault_info *inf = fault_info + (esr & 63);
- return inf->name;
-}
-
/*
* Dispatch a data abort to the relevant handler.
*/
asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr,
struct pt_regs *regs)
{
- const struct fault_info *inf = fault_info + (esr & 63);
+ const struct fault_info *inf = esr_to_fault_info(esr);
struct siginfo info;

if (!inf->fn(addr, esr, regs))

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