From a6972f8bd2b6af5af070c76b8178f8fa87d44cb9 Mon Sep 17 00:00:00 2001 From: "Maciej W. Rozycki" Date: Mon, 11 Dec 2017 22:53:14 +0000 Subject: MIPS: Consistently handle buffer counter with PTRACE_SETREGSET commit 80b3ffce0196ea50068885d085ff981e4b8396f4 upstream. Update commit d614fd58a283 ("mips/ptrace: Preserve previous registers for short regset write") bug and consistently consume all data supplied to `fpr_set_msa' with the ptrace(2) PTRACE_SETREGSET request, such that a zero data buffer counter is returned where insufficient data has been given to fill a whole number of FP general registers. In reality this is not going to happen, as the caller is supposed to only supply data covering a whole number of registers and it is verified in `ptrace_regset' and again asserted in `fpr_set', however structuring code such that the presence of trailing partial FP general register data causes `fpr_set_msa' to return with a non-zero data buffer counter makes it appear that this trailing data will be used if there are subsequent writes made to FP registers, which is going to be the case with the FCSR once the missing write to that register has been fixed. Fixes: d614fd58a283 ("mips/ptrace: Preserve previous registers for short regset write") Signed-off-by: Maciej W. Rozycki Cc: James Hogan Cc: Paul Burton Cc: Alex Smith Cc: Dave Martin Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/17927/ Signed-off-by: Ralf Baechle Signed-off-by: Greg Kroah-Hartman --- arch/mips/kernel/ptrace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/mips') diff --git a/arch/mips/kernel/ptrace.c b/arch/mips/kernel/ptrace.c index cd05e34995d4..a24a2e7ccb10 100644 --- a/arch/mips/kernel/ptrace.c +++ b/arch/mips/kernel/ptrace.c @@ -524,7 +524,7 @@ static int fpr_set_msa(struct task_struct *target, int err; BUILD_BUG_ON(sizeof(fpr_val) != sizeof(elf_fpreg_t)); - for (i = 0; i < NUM_FPU_REGS && *count >= sizeof(elf_fpreg_t); i++) { + for (i = 0; i < NUM_FPU_REGS && *count > 0; i++) { err = user_regset_copyin(pos, count, kbuf, ubuf, &fpr_val, i * sizeof(elf_fpreg_t), (i + 1) * sizeof(elf_fpreg_t)); -- cgit v1.2.3