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authorMaciej W. Rozycki <macro@mips.com>2017-12-11 22:52:15 +0000
committerRalf Baechle <ralf@linux-mips.org>2017-12-12 19:11:53 +0100
commitdc24d0edf33c3e15099688b6bbdf7bdc24bf6e91 (patch)
treed81454989e98c8925d871d8decd27aca3a0597af /arch/mips/kernel/ptrace.c
parenta03fe72572c12e98f4173f8a535f32468e48b6ec (diff)
MIPS: Guard against any partial write attempt with PTRACE_SETREGSET
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>
Diffstat (limited to 'arch/mips/kernel/ptrace.c')
-rw-r--r--arch/mips/kernel/ptrace.c12
1 files changed, 11 insertions, 1 deletions
diff --git a/arch/mips/kernel/ptrace.c b/arch/mips/kernel/ptrace.c
index 62e8ffd9370a..7fcadaaf330f 100644
--- a/arch/mips/kernel/ptrace.c
+++ b/arch/mips/kernel/ptrace.c
@@ -516,7 +516,15 @@ 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,
@@ -524,6 +532,8 @@ static int fpr_set(struct task_struct *target,
{
int err;
+ BUG_ON(count % sizeof(elf_fpreg_t));
+
/* XXX fcr31 */
init_fp_ctx(target);