[ 09/82] ARM: fix scheduling while atomic warning in alignment handling code

Ben Hutchings
2013-03-18T04:30:30Z

From: Russell King <rmk+kernel@arm.linux.org.uk>

commit b255188f90e2bade1bd11a986dd1ca4861869f4d upstream.

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().

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/arm/mm/alignment.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)

--- a/arch/arm/mm/alignment.c
+++ b/arch/arm/mm/alignment.c
@@ -749,7 +749,6 @@ do_alignment(unsigned long addr, unsigne
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, unsigne

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, unsigne
}
}
} else
- fault = __get_user(instr, (u32 *)instrptr);
- set_fs(fs);
+ fault = probe_kernel_address(instrptr, instr);

if (fault) {
type = TYPE_FAULT;