[PATCH 0/3] ARM/arm64: ptrace: fix unaligned hardware breakpoint validation for 32bit

[b10902118]

PTRACE_SETREGSET and PTRACE_SETHBPREGS fail when setting a hardware
breakpoint on a non-4-byte aligned address with a valid length to
a 32-bit tracee. The length should be valid as long as the range
started from the address is within one aligned 4 bytes.


The Cause:

The kernel modifies a breakpoint's addr and ctrl separately, but
each modification comes with validation, so the first validation
sees the user-provided addr and old ctrl (and vice versa for
PTRACE_SETHBPREGS). This combination can be invalid if the address
is unaligned and the control's length is too long (ex: the 4-byte
default).

The kernel only checks the alignment for 32-bit tracees, so this only
happens to them.


The Fix:

1. Fix PTRACE_SETREGSET by modifying addr and ctrl together.

2. Mitigate PTRACE_SETHBPREGS by minimizing default length.

   This cannot be fixed without removing or relaxing the alignment
   check because partially modified breakpoints are unavoidable for
   PTRACE_SETHBPREGS, which receives either addr or ctrl per call.


b10902118 (3):
  arm64: ptrace: fix hw_break_set() by setting addr and ctrl together
  arm64: ptrace: minimize default bp_len for hw breakpoints to pass
    check
  ARM: ptrace: minimize default bp_len for hw breakpoints to pass check

 arch/arm/kernel/ptrace.c   | 16 ++++++++++++-
 arch/arm64/kernel/ptrace.c | 49 ++++++++++++++++++++++++++++++++------
 2 files changed, 57 insertions(+), 8 deletions(-)

-- 
2.50.1