[PATCH 3.16 238/370] arm64/ptrace: Reject attempts to set incomplete hardware breakpoint fields

Ben Hutchings
2017-03-10T13:54:16Z

From: Dave Martin <Dave.Martin@arm.com>

commit ad9e202aa1ce571b1d7fed969d06f66067f8a086 upstream.

We cannot preserve partial fields for hardware breakpoints, because
the values written by userspace to the hardware breakpoint
registers can't subsequently be recovered intact from the hardware.

So, just reject attempts to write incomplete fields with -EINVAL.

Fixes: 478fcb2cdb23 ("arm64: Debugging support")
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Acked-by: Will Deacon <Will.Deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/arm64/kernel/ptrace.c | 4 ++++
1 file changed, 4 insertions(+)

--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -446,6 +446,8 @@ static int hw_break_set(struct task_stru
/* (address, ctrl) registers */
limit = regset->n * regset->size;
while (count && offset < limit) {
+ if (count < PTRACE_HBP_ADDR_SZ)
+ return -EINVAL;
ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &addr,
offset, offset + PTRACE_HBP_ADDR_SZ);
if (ret)
@@ -455,6 +457,8 @@ static int hw_break_set(struct task_stru
return ret;
offset += PTRACE_HBP_ADDR_SZ;

+ if (!count)
+ break;
ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &ctrl,
offset, offset + PTRACE_HBP_CTRL_SZ);
if (ret)