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8b3c569a39
Commit 1400eb6 (MIPS: r4k,octeon,r2300: stack protector: change canary
per task) was merged in v3.11 and introduced assembly in the MIPS resume
functions to update the value of the current canary in
__stack_chk_guard. However it used PTR_L resulting in a load of the
canary value, instead of PTR_LA to construct its address. The value is
intended to be random but is then treated as an address in the
subsequent LONG_S (store).
This was observed to cause a fault and panic:
CPU 0 Unable to handle kernel paging request at virtual address 139fea20, epc == 8000cc0c, ra == 8034f2a4
Oops[#1]:
...
$24 : 139fea20 1e1f7cb6
...
Call Trace:
[<8000cc0c>] resume+0xac/0x118
[<8034f2a4>] __schedule+0x5f8/0x78c
[<8034f4e0>] schedule_preempt_disabled+0x20/0x2c
[<80348eec>] rest_init+0x74/0x84
[<804dc990>] start_kernel+0x43c/0x454
Code: 3c18804b 8f184030 8cb901f8 <af190000> 00c0e021 8cb002f0 8cb102f4 8cb202f8 8cb302fc
This can also be forced by modifying
arch/mips/include/asm/stackprotector.h so that the default
__stack_chk_guard value is more likely to be a bad (or unaligned)
pointer.
Fix it to use PTR_LA instead, to load the address of the canary value,
which the LONG_S can then use to write into it.
Reported-by: bobjones (via #mipslinux on IRC)
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Gregory Fong <gregory.0xf0@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/6026/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
168 lines
3.3 KiB
ArmAsm
168 lines
3.3 KiB
ArmAsm
/*
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* r2300_switch.S: R2300 specific task switching code.
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*
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* Copyright (C) 1994, 1995, 1996, 1999 by Ralf Baechle
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* Copyright (C) 1994, 1995, 1996 by Andreas Busse
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*
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* Multi-cpu abstraction and macros for easier reading:
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* Copyright (C) 1996 David S. Miller (davem@davemloft.net)
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*
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* Further modifications to make this work:
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* Copyright (c) 1998-2000 Harald Koerfgen
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*/
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#include <asm/asm.h>
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#include <asm/cachectl.h>
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#include <asm/fpregdef.h>
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#include <asm/mipsregs.h>
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#include <asm/asm-offsets.h>
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#include <asm/regdef.h>
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#include <asm/stackframe.h>
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#include <asm/thread_info.h>
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#include <asm/asmmacro.h>
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.set mips1
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.align 5
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/*
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* Offset to the current process status flags, the first 32 bytes of the
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* stack are not used.
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*/
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#define ST_OFF (_THREAD_SIZE - 32 - PT_SIZE + PT_STATUS)
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/*
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* FPU context is saved iff the process has used it's FPU in the current
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* time slice as indicated by TIF_USEDFPU. In any case, the CU1 bit for user
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* space STATUS register should be 0, so that a process *always* starts its
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* userland with FPU disabled after each context switch.
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*
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* FPU will be enabled as soon as the process accesses FPU again, through
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* do_cpu() trap.
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*/
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/*
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* task_struct *resume(task_struct *prev, task_struct *next,
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* struct thread_info *next_ti, int usedfpu)
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*/
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LEAF(resume)
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mfc0 t1, CP0_STATUS
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sw t1, THREAD_STATUS(a0)
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cpu_save_nonscratch a0
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sw ra, THREAD_REG31(a0)
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beqz a3, 1f
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PTR_L t3, TASK_THREAD_INFO(a0)
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/*
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* clear saved user stack CU1 bit
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*/
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lw t0, ST_OFF(t3)
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li t1, ~ST0_CU1
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and t0, t0, t1
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sw t0, ST_OFF(t3)
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fpu_save_single a0, t0 # clobbers t0
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1:
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#if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP)
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PTR_LA t8, __stack_chk_guard
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LONG_L t9, TASK_STACK_CANARY(a1)
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LONG_S t9, 0(t8)
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#endif
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/*
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* The order of restoring the registers takes care of the race
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* updating $28, $29 and kernelsp without disabling ints.
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*/
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move $28, a2
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cpu_restore_nonscratch a1
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addiu t1, $28, _THREAD_SIZE - 32
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sw t1, kernelsp
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mfc0 t1, CP0_STATUS /* Do we really need this? */
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li a3, 0xff01
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and t1, a3
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lw a2, THREAD_STATUS(a1)
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nor a3, $0, a3
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and a2, a3
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or a2, t1
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mtc0 a2, CP0_STATUS
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move v0, a0
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jr ra
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END(resume)
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/*
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* Save a thread's fp context.
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*/
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LEAF(_save_fp)
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fpu_save_single a0, t1 # clobbers t1
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jr ra
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END(_save_fp)
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/*
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* Restore a thread's fp context.
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*/
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LEAF(_restore_fp)
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fpu_restore_single a0, t1 # clobbers t1
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jr ra
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END(_restore_fp)
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/*
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* Load the FPU with signalling NANS. This bit pattern we're using has
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* the property that no matter whether considered as single or as double
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* precision represents signaling NANS.
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*
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* We initialize fcr31 to rounding to nearest, no exceptions.
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*/
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#define FPU_DEFAULT 0x00000000
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LEAF(_init_fpu)
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mfc0 t0, CP0_STATUS
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li t1, ST0_CU1
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or t0, t1
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mtc0 t0, CP0_STATUS
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li t1, FPU_DEFAULT
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ctc1 t1, fcr31
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li t0, -1
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mtc1 t0, $f0
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mtc1 t0, $f1
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mtc1 t0, $f2
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mtc1 t0, $f3
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mtc1 t0, $f4
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mtc1 t0, $f5
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mtc1 t0, $f6
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mtc1 t0, $f7
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mtc1 t0, $f8
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mtc1 t0, $f9
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mtc1 t0, $f10
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mtc1 t0, $f11
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mtc1 t0, $f12
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mtc1 t0, $f13
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mtc1 t0, $f14
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mtc1 t0, $f15
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mtc1 t0, $f16
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mtc1 t0, $f17
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mtc1 t0, $f18
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mtc1 t0, $f19
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mtc1 t0, $f20
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mtc1 t0, $f21
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mtc1 t0, $f22
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mtc1 t0, $f23
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mtc1 t0, $f24
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mtc1 t0, $f25
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mtc1 t0, $f26
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mtc1 t0, $f27
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mtc1 t0, $f28
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mtc1 t0, $f29
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mtc1 t0, $f30
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mtc1 t0, $f31
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jr ra
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END(_init_fpu)
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