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ARM: spectre-v1: fix syscall entry 

Commit 10573ae547 upstream.

Prevent speculation at the syscall table decoding by clamping the index
used to zero on invalid system call numbers, and using the csdb
speculative barrier.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Boot-tested-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: David A. Long <dave.long@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
pull/10/head
Russell King 2018-10-15 11:32:12 -04:00 committed by Greg Kroah-Hartman
parent 4186f7cfa1
commit b690ec0dc7
2 changed files with 32 additions and 11 deletions
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18
arch/arm/kernel/entry-common.S
View File

@ -241,9 +241,7 @@ local_restart:
tst r10, #_TIF_SYSCALL_WORK @ are we tracing syscalls?
bne __sys_trace
cmp scno, #NR_syscalls @ check upper syscall limit
badr lr, ret_fast_syscall @ return address
ldrcc pc, [tbl, scno, lsl #2] @ call sys_* routine
invoke_syscall tbl, scno, r10, ret_fast_syscall
add r1, sp, #S_OFF
2: cmp scno, #(__ARM_NR_BASE - __NR_SYSCALL_BASE)
@ -277,14 +275,8 @@ __sys_trace:
mov r1, scno
add r0, sp, #S_OFF
bl syscall_trace_enter
badr lr, __sys_trace_return @ return address
mov scno, r0 @ syscall number (possibly new)
add r1, sp, #S_R0 + S_OFF @ pointer to regs
cmp scno, #NR_syscalls @ check upper syscall limit
ldmccia r1, {r0 - r6} @ have to reload r0 - r6
stmccia sp, {r4, r5} @ and update the stack args
ldrcc pc, [tbl, scno, lsl #2] @ call sys_* routine
mov scno, r0
invoke_syscall tbl, scno, r10, __sys_trace_return, reload=1
cmp scno, #-1 @ skip the syscall?
bne 2b
add sp, sp, #S_OFF @ restore stack
@ -362,6 +354,10 @@ sys_syscall:
bic scno, r0, #__NR_OABI_SYSCALL_BASE
cmp scno, #__NR_syscall - __NR_SYSCALL_BASE
cmpne scno, #NR_syscalls @ check range
#ifdef CONFIG_CPU_SPECTRE
movhs scno, #0
csdb
#endif
stmloia sp, {r5, r6} @ shuffle args
movlo r0, r1
movlo r1, r2

25
arch/arm/kernel/entry-header.S
View File

@ -378,6 +378,31 @@
#endif
.endm
.macro invoke_syscall, table, nr, tmp, ret, reload=0
#ifdef CONFIG_CPU_SPECTRE
mov \tmp, \nr
cmp \tmp, #NR_syscalls @ check upper syscall limit
movcs \tmp, #0
csdb
badr lr, \ret @ return address
.if \reload
add r1, sp, #S_R0 + S_OFF @ pointer to regs
ldmccia r1, {r0 - r6} @ reload r0-r6
stmccia sp, {r4, r5} @ update stack arguments
.endif
ldrcc pc, [\table, \tmp, lsl #2] @ call sys_* routine
#else
cmp \nr, #NR_syscalls @ check upper syscall limit
badr lr, \ret @ return address
.if \reload
add r1, sp, #S_R0 + S_OFF @ pointer to regs
ldmccia r1, {r0 - r6} @ reload r0-r6
stmccia sp, {r4, r5} @ update stack arguments
.endif
ldrcc pc, [\table, \nr, lsl #2] @ call sys_* routine
#endif
.endm
/*
* These are the registers used in the syscall handler, and allow us to
* have in theory up to 7 arguments to a function - r0 to r6.