4.18-stable review patch. If anyone has any objections, please let me know.
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From: Mark Rutland mark.rutland@arm.com
[ Upstream commit 14d6e289a89780377f8bb09de8926d3c62d763cd ]
It's possible for userspace to control idx. Sanitize idx when using it as an array index, to inhibit the potential spectre-v1 write gadget.
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 Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/kernel/ptrace.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-)
--- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -277,19 +277,22 @@ static int ptrace_hbp_set_event(unsigned
switch (note_type) { case NT_ARM_HW_BREAK: - if (idx < ARM_MAX_BRP) { - tsk->thread.debug.hbp_break[idx] = bp; - err = 0; - } + if (idx >= ARM_MAX_BRP) + goto out; + idx = array_index_nospec(idx, ARM_MAX_BRP); + tsk->thread.debug.hbp_break[idx] = bp; + err = 0; break; case NT_ARM_HW_WATCH: - if (idx < ARM_MAX_WRP) { - tsk->thread.debug.hbp_watch[idx] = bp; - err = 0; - } + if (idx >= ARM_MAX_WRP) + goto out; + idx = array_index_nospec(idx, ARM_MAX_WRP); + tsk->thread.debug.hbp_watch[idx] = bp; + err = 0; break; }
+out: return err; }