ARM: fix scheduling while atomic warning in alignment handling code

Paolo Pisati reports that IPv6 triggers this warning:

BUG: scheduling while atomic: swapper/0/0/0x40000100
Modules linked in:
[<c001b1c4>] (unwind_backtrace+0x0/0xf0) from [<c0503c5c>] (__schedule_bug+0x48/0x5c)
[<c0503c5c>] (__schedule_bug+0x48/0x5c) from [<c0508608>] (__schedule+0x700/0x740)
[<c0508608>] (__schedule+0x700/0x740) from [<c007007c>] (__cond_resched+0x24/0x34)
[<c007007c>] (__cond_resched+0x24/0x34) from [<c05086dc>] (_cond_resched+0x3c/0x44)
[<c05086dc>] (_cond_resched+0x3c/0x44) from [<c0021f6c>] (do_alignment+0x178/0x78c)
[<c0021f6c>] (do_alignment+0x178/0x78c) from [<c00083e0>] (do_DataAbort+0x34/0x98)
[<c00083e0>] (do_DataAbort+0x34/0x98) from [<c0509a60>] (__dabt_svc+0x40/0x60)
Exception stack(0xc0763d70 to 0xc0763db8)
3d60:                                     e97e805e e97e806e 2c000000 11000000
3d80: ea86bb00 0000002c 00000011 e97e807e c076d2a8 e97e805e e97e806e 0000002c
3da0: 3d000000 c0763dbc c04b98fc c02a8490 00000113 ffffffff
[<c0509a60>] (__dabt_svc+0x40/0x60) from [<c02a8490>] (__csum_ipv6_magic+0x8/0xc8)

Fix this by using probe_kernel_address() stead of __get_user().

Cc: <stable@vger.kernel.org>
Reported-by: Paolo Pisati <p.pisati@gmail.com>
Tested-by: Paolo Pisati <p.pisati@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 4 insertions, 7 deletions

diff --git a/arch/arm/mm/alignment.c b/arch/arm/mm/alignment.c
index b820edaf3184..db26e2e543f4 100644
--- a/arch/arm/mm/alignment.c
+++ b/arch/arm/mm/alignment.c
@@ -749,7 +749,6 @@ do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
         unsigned long instr = 0, instrptr;
         int (*handler)(unsigned long addr, unsigned long instr, struct pt_regs *regs);
         unsigned int type;
-        mm_segment_t fs;
         unsigned int fault;
         u16 tinstr = 0;
         int isize = 4;
@@ -760,16 +759,15 @@ do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 
         instrptr = instruction_pointer(regs);
 
-        fs = get_fs();
-        set_fs(KERNEL_DS);
         if (thumb_mode(regs)) {
-                fault = __get_user(tinstr, (u16 *)(instrptr & ~1));
+                u16 *ptr = (u16 *)(instrptr & ~1);
+                fault = probe_kernel_address(ptr, tinstr);
                 if (!fault) {
                         if (cpu_architecture() >= CPU_ARCH_ARMv7 &&
                             IS_T32(tinstr)) {
                                 /* Thumb-2 32-bit */
                                 u16 tinst2 = 0;
-                                fault = __get_user(tinst2, (u16 *)(instrptr+2));
+                                fault = probe_kernel_address(ptr + 1, tinst2);
                                 instr = (tinstr << 16) | tinst2;
                                 thumb2_32b = 1;
                         } else {
@@ -778,8 +776,7 @@ do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
                         }
                 }
         } else
-                fault = __get_user(instr, (u32 *)instrptr);
-        set_fs(fs);
+                fault = probe_kernel_address(instrptr, instr);
 
         if (fault) {
                 type = TYPE_FAULT;