From: "Maciej W. Rozycki" macro@mips.com
This patch has been added to the 4.1 stable tree. If you have any objections, please let us know.
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[ Upstream commit dc24d0edf33c3e15099688b6bbdf7bdc24bf6e91 ]
Complement commit d614fd58a283 ("mips/ptrace: Preserve previous registers for short regset write") and ensure that no partial register write attempt is made with PTRACE_SETREGSET, as we do not preinitialize any temporaries used to hold incoming register data and consequently random data could be written.
It is the responsibility of the caller, such as `ptrace_regset', to arrange for writes to span whole registers only, so here we only assert that it has indeed happened.
Signed-off-by: Maciej W. Rozycki macro@mips.com Fixes: 72b22bbad1e7 ("MIPS: Don't assume 64-bit FP registers for FP regset") Cc: James Hogan james.hogan@mips.com Cc: Paul Burton Paul.Burton@mips.com Cc: Alex Smith alex@alex-smith.me.uk Cc: Dave Martin Dave.Martin@arm.com Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org # v3.15+ Patchwork: https://patchwork.linux-mips.org/patch/17926/ Signed-off-by: Ralf Baechle ralf@linux-mips.org Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- arch/mips/kernel/ptrace.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/arch/mips/kernel/ptrace.c b/arch/mips/kernel/ptrace.c index 6d3bdd9af8af..30eaf03e6679 100644 --- a/arch/mips/kernel/ptrace.c +++ b/arch/mips/kernel/ptrace.c @@ -535,7 +535,15 @@ static int fpr_set_msa(struct task_struct *target, return 0; }
-/* Copy the supplied NT_PRFPREG buffer to the floating-point context. */ +/* + * Copy the supplied NT_PRFPREG buffer to the floating-point context. + * + * We optimize for the case where `count % sizeof(elf_fpreg_t) == 0', + * which is supposed to have been guaranteed by the kernel before + * calling us, e.g. in `ptrace_regset'. We enforce that requirement, + * so that we can safely avoid preinitializing temporaries for + * partial register writes. + */ static int fpr_set(struct task_struct *target, const struct user_regset *regset, unsigned int pos, unsigned int count, @@ -543,6 +551,8 @@ static int fpr_set(struct task_struct *target, { int err;
+ BUG_ON(count % sizeof(elf_fpreg_t)); + /* XXX fcr31 */
init_fp_ctx(target);