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arm64: fix possible spectre-v1 in ptrace_hbp_get_event() 

It's possible for userspace to control idx. Sanitize idx when using it
as an array index.

Found by smatch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
hifive-unleashed-5.1
Mark Rutland 2018-04-25 17:13:40 +01:00 committed by Will Deacon
parent ad40bdafb4
commit 19791a7ca6
1 changed files with 10 additions and 4 deletions
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14
arch/arm64/kernel/ptrace.c
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@ -25,6 +25,7 @@
#include <linux/sched/signal.h>
#include <linux/sched/task_stack.h>
#include <linux/mm.h>
#include <linux/nospec.h>
#include <linux/smp.h>
#include <linux/ptrace.h>
#include <linux/user.h>
@ -249,15 +250,20 @@ static struct perf_event *ptrace_hbp_get_event(unsigned int note_type,
switch (note_type) {
case NT_ARM_HW_BREAK:
if (idx < ARM_MAX_BRP)
bp = tsk->thread.debug.hbp_break[idx];
if (idx >= ARM_MAX_BRP)
goto out;
idx = array_index_nospec(idx, ARM_MAX_BRP);
bp = tsk->thread.debug.hbp_break[idx];
break;
case NT_ARM_HW_WATCH:
if (idx < ARM_MAX_WRP)
bp = tsk->thread.debug.hbp_watch[idx];
if (idx >= ARM_MAX_WRP)
goto out;
idx = array_index_nospec(idx, ARM_MAX_WRP);
bp = tsk->thread.debug.hbp_watch[idx];
break;
}
out:
return bp;
}