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alistair23-linux/arch/score/kernel/entry.S
Dan Rosenberg c25a785d66 score: fix off-by-one index into syscall table 
If the provided system call number is equal to __NR_syscalls, the
current check will pass and a function pointer just after the system
call table may be called, since sys_call_table is an array with total
size __NR_syscalls.

Whether or not this is a security bug depends on what the compiler puts
immediately after the system call table.  It's likely that this won't do
anything bad because there is an additional NULL check on the syscall
entry, but if there happens to be a non-NULL value immediately after the
system call table, this may result in local privilege escalation.

Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
Cc: <stable@vger.kernel.org>
Cc: Chen Liqin <liqin.chen@sunplusct.com>
Cc: Lennox Wu <lennox.wu@gmail.com>
Cc: Eugene Teo <eugeneteo@kernel.sg>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-01-23 08:38:49 -08:00

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/*
* arch/score/kernel/entry.S
*
* Score Processor version.
*
* Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
* Chen Liqin <liqin.chen@sunplusct.com>
* Lennox Wu <lennox.wu@sunplusct.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see the file COPYING, or write
* to the Free Software Foundation, Inc.,
* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <linux/err.h>
#include <linux/init.h>
#include <linux/linkage.h>
#include <asm/asmmacro.h>
#include <asm/thread_info.h>
#include <asm/unistd.h>
/*
* disable interrupts.
*/
.macro disable_irq
mfcr r8, cr0
srli r8, r8, 1
slli r8, r8, 1
mtcr r8, cr0
nop
nop
nop
nop
nop
.endm
/*
* enable interrupts.
*/
.macro enable_irq
mfcr r8, cr0
ori r8, 1
mtcr r8, cr0
nop
nop
nop
nop
nop
.endm
__INIT
ENTRY(debug_exception_vector)
nop!
nop!
nop!
nop!
nop!
nop!
nop!
nop!
ENTRY(general_exception_vector) # should move to addr 0x200
j general_exception
nop!
nop!
nop!
nop!
nop!
nop!
ENTRY(interrupt_exception_vector) # should move to addr 0x210
j interrupt_exception
nop!
nop!
nop!
nop!
nop!
nop!
.section ".text", "ax"
.align 2;
general_exception:
mfcr r31, cr2
nop
la r30, exception_handlers
andi r31, 0x1f # get ecr.exc_code
slli r31, r31, 2
add r30, r30, r31
lw r30, [r30]
br r30
interrupt_exception:
SAVE_ALL
mfcr r4, cr2
nop
lw r16, [r28, TI_REGS]
sw r0, [r28, TI_REGS]
la r3, ret_from_irq
srli r4, r4, 18 # get ecr.ip[7:2], interrupt No.
mv r5, r0
j do_IRQ
ENTRY(handle_nmi) # NMI #1
SAVE_ALL
mv r4, r0
la r8, nmi_exception_handler
brl r8
j restore_all
ENTRY(handle_adelinsn) # AdEL-instruction #2
SAVE_ALL
mfcr r8, cr6
nop
nop
sw r8, [r0, PT_EMA]
mv r4, r0
la r8, do_adelinsn
brl r8
mv r4, r0
j ret_from_exception
nop
ENTRY(handle_ibe) # BusEL-instruction #5
SAVE_ALL
mv r4, r0
la r8, do_be
brl r8
mv r4, r0
j ret_from_exception
nop
ENTRY(handle_pel) # P-EL #6
SAVE_ALL
mv r4, r0
la r8, do_pel
brl r8
mv r4, r0
j ret_from_exception
nop
ENTRY(handle_ccu) # CCU #8
SAVE_ALL
mv r4, r0
la r8, do_ccu
brl r8
mv r4, r0
j ret_from_exception
nop
ENTRY(handle_ri) # RI #9
SAVE_ALL
mv r4, r0
la r8, do_ri
brl r8
mv r4, r0
j ret_from_exception
nop
ENTRY(handle_tr) # Trap #10
SAVE_ALL
mv r4, r0
la r8, do_tr
brl r8
mv r4, r0
j ret_from_exception
nop
ENTRY(handle_adedata) # AdES-instruction #12
SAVE_ALL
mfcr r8, cr6
nop
nop
sw r8, [r0, PT_EMA]
mv r4, r0
la r8, do_adedata
brl r8
mv r4, r0
j ret_from_exception
nop
ENTRY(handle_cee) # CeE #16
SAVE_ALL
mv r4, r0
la r8, do_cee
brl r8
mv r4, r0
j ret_from_exception
nop
ENTRY(handle_cpe) # CpE #17
SAVE_ALL
mv r4, r0
la r8, do_cpe
brl r8
mv r4, r0
j ret_from_exception
nop
ENTRY(handle_dbe) # BusEL-data #18
SAVE_ALL
mv r4, r0
la r8, do_be
brl r8
mv r4, r0
j ret_from_exception
nop
ENTRY(handle_reserved) # others
SAVE_ALL
mv r4, r0
la r8, do_reserved
brl r8
mv r4, r0
j ret_from_exception
nop
#ifndef CONFIG_PREEMPT
#define resume_kernel restore_all
#else
#define __ret_from_irq ret_from_exception
#endif
.align 2
#ifndef CONFIG_PREEMPT
ENTRY(ret_from_exception)
disable_irq # preempt stop
nop
j __ret_from_irq
nop
#endif
ENTRY(ret_from_irq)
sw r16, [r28, TI_REGS]
ENTRY(__ret_from_irq)
lw r8, [r0, PT_PSR] # returning to kernel mode?
andri.c r8, r8, KU_USER
beq resume_kernel
resume_userspace:
disable_irq
lw r6, [r28, TI_FLAGS] # current->work
li r8, _TIF_WORK_MASK
and.c r8, r8, r6 # ignoring syscall_trace
bne work_pending
nop
j restore_all
nop
#ifdef CONFIG_PREEMPT
resume_kernel:
disable_irq
lw r8, [r28, TI_PRE_COUNT]
cmpz.c r8
bne r8, restore_all
need_resched:
lw r8, [r28, TI_FLAGS]
andri.c r9, r8, _TIF_NEED_RESCHED
beq restore_all
lw r8, [r28, PT_PSR] # Interrupts off?
andri.c r8, r8, 1
beq restore_all
bl preempt_schedule_irq
nop
j need_resched
nop
#endif
ENTRY(ret_from_fork)
bl schedule_tail # r4=struct task_struct *prev
ENTRY(syscall_exit)
nop
disable_irq
lw r6, [r28, TI_FLAGS] # current->work
li r8, _TIF_WORK_MASK
and.c r8, r6, r8
bne syscall_exit_work
ENTRY(restore_all) # restore full frame
RESTORE_ALL_AND_RET
work_pending:
andri.c r8, r6, _TIF_NEED_RESCHED # r6 is preloaded with TI_FLAGS
beq work_notifysig
work_resched:
bl schedule
nop
disable_irq
lw r6, [r28, TI_FLAGS]
li r8, _TIF_WORK_MASK
and.c r8, r6, r8 # is there any work to be done
# other than syscall tracing?
beq restore_all
andri.c r8, r6, _TIF_NEED_RESCHED
bne work_resched
work_notifysig:
mv r4, r0
li r5, 0
bl do_notify_resume # r6 already loaded
nop
j resume_userspace
nop
ENTRY(syscall_exit_work)
li r8, _TIF_SYSCALL_TRACE
and.c r8, r8, r6 # r6 is preloaded with TI_FLAGS
beq work_pending # trace bit set?
nop
enable_irq
mv r4, r0
li r5, 1
bl do_syscall_trace
nop
b resume_userspace
nop
.macro save_context reg
sw r12, [\reg, THREAD_REG12];
sw r13, [\reg, THREAD_REG13];
sw r14, [\reg, THREAD_REG14];
sw r15, [\reg, THREAD_REG15];
sw r16, [\reg, THREAD_REG16];
sw r17, [\reg, THREAD_REG17];
sw r18, [\reg, THREAD_REG18];
sw r19, [\reg, THREAD_REG19];
sw r20, [\reg, THREAD_REG20];
sw r21, [\reg, THREAD_REG21];
sw r29, [\reg, THREAD_REG29];
sw r2, [\reg, THREAD_REG2];
sw r0, [\reg, THREAD_REG0]
.endm
.macro restore_context reg
lw r12, [\reg, THREAD_REG12];
lw r13, [\reg, THREAD_REG13];
lw r14, [\reg, THREAD_REG14];
lw r15, [\reg, THREAD_REG15];
lw r16, [\reg, THREAD_REG16];
lw r17, [\reg, THREAD_REG17];
lw r18, [\reg, THREAD_REG18];
lw r19, [\reg, THREAD_REG19];
lw r20, [\reg, THREAD_REG20];
lw r21, [\reg, THREAD_REG21];
lw r29, [\reg, THREAD_REG29];
lw r0, [\reg, THREAD_REG0];
lw r2, [\reg, THREAD_REG2];
lw r3, [\reg, THREAD_REG3]
.endm
/*
* task_struct *resume(task_struct *prev, task_struct *next,
* struct thread_info *next_ti)
*/
ENTRY(resume)
mfcr r9, cr0
nop
nop
sw r9, [r4, THREAD_PSR]
save_context r4
sw r3, [r4, THREAD_REG3]
mv r28, r6
restore_context r5
mv r8, r6
addi r8, KERNEL_STACK_SIZE
subi r8, 32
la r9, kernelsp;
sw r8, [r9];
mfcr r9, cr0
ldis r7, 0x00ff
nop
and r9, r9, r7
lw r6, [r5, THREAD_PSR]
not r7, r7
and r6, r6, r7
or r6, r6, r9
mtcr r6, cr0
nop; nop; nop; nop; nop
br r3
ENTRY(handle_sys)
SAVE_ALL
sw r8, [r0, 16] # argument 5 from user r8
sw r9, [r0, 20] # argument 6 from user r9
enable_irq
sw r4, [r0, PT_ORIG_R4] #for restart syscall
sw r7, [r0, PT_ORIG_R7] #for restart syscall
sw r27, [r0, PT_IS_SYSCALL] # it from syscall
lw r9, [r0, PT_EPC] # skip syscall on return
addi r9, 4
sw r9, [r0, PT_EPC]
cmpi.c r27, __NR_syscalls # check syscall number
bgeu illegal_syscall
slli r8, r27, 2 # get syscall routine
la r11, sys_call_table
add r11, r11, r8
lw r10, [r11] # get syscall entry
cmpz.c r10
beq illegal_syscall
lw r8, [r28, TI_FLAGS]
li r9, _TIF_SYSCALL_TRACE
and.c r8, r8, r9
bne syscall_trace_entry
brl r10 # Do The Real system call
cmpi.c r4, 0
blt 1f
ldi r8, 0
sw r8, [r0, PT_R7]
b 2f
1:
cmpi.c r4, -MAX_ERRNO - 1
ble 2f
ldi r8, 0x1;
sw r8, [r0, PT_R7]
neg r4, r4
2:
sw r4, [r0, PT_R4] # save result
syscall_return:
disable_irq
lw r6, [r28, TI_FLAGS] # current->work
li r8, _TIF_WORK_MASK
and.c r8, r6, r8
bne syscall_return_work
j restore_all
syscall_return_work:
j syscall_exit_work
syscall_trace_entry:
mv r16, r10
mv r4, r0
li r5, 0
bl do_syscall_trace
mv r8, r16
lw r4, [r0, PT_R4] # Restore argument registers
lw r5, [r0, PT_R5]
lw r6, [r0, PT_R6]
lw r7, [r0, PT_R7]
brl r8
li r8, -MAX_ERRNO - 1
sw r8, [r0, PT_R7] # set error flag
neg r4, r4 # error
sw r4, [r0, PT_R0] # set flag for syscall
# restarting
1: sw r4, [r0, PT_R2] # result
j syscall_exit
illegal_syscall:
ldi r4, -ENOSYS # error
sw r4, [r0, PT_ORIG_R4]
sw r4, [r0, PT_R4]
ldi r9, 1 # set error flag
sw r9, [r0, PT_R7]
j syscall_return
ENTRY(sys_execve)
mv r4, r0
la r8, score_execve
br r8
ENTRY(sys_clone)
mv r4, r0
la r8, score_clone
br r8
ENTRY(sys_rt_sigreturn)
mv r4, r0
la r8, score_rt_sigreturn
br r8
ENTRY(sys_sigaltstack)
mv r4, r0
la r8, score_sigaltstack
br r8
#ifdef __ARCH_WANT_SYSCALL_DEPRECATED
ENTRY(sys_fork)
mv r4, r0
la r8, score_fork
br r8
ENTRY(sys_vfork)
mv r4, r0
la r8, score_vfork
br r8
#endif /* __ARCH_WANT_SYSCALL_DEPRECATED */
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