[PATCH 3.18 v2 2/5] MIPS: Guard against any partial write attempt with PTRACE_SETREGSET

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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@xxxxxxxx>
Fixes: 72b22bbad1e7 ("MIPS: Don't assume 64-bit FP registers for FP regset")
Cc: James Hogan <james.hogan@xxxxxxxx>
Cc: Paul Burton <Paul.Burton@xxxxxxxx>
Cc: Alex Smith <alex@xxxxxxxxxxxxxxxx>
Cc: Dave Martin <Dave.Martin@xxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx # v3.15+
Patchwork: https://patchwork.linux-mips.org/patch/17926/
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
---
Hi,

 This is a (mechanically regenerated) version of commit dc24d0edf33c for
3.18-stable and before.  No functional changes.  Please apply.

  Maciej

---
 arch/mips/kernel/ptrace.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

linux-mips-nt-prfpreg-size-bug.diff
Index: linux-stable-el/arch/mips/kernel/ptrace.c
===================================================================
--- linux-stable-el.orig/arch/mips/kernel/ptrace.c	2018-01-10 20:13:31.900045000 +0000
+++ linux-stable-el/arch/mips/kernel/ptrace.c	2018-01-10 20:13:33.337064000 +0000
@@ -497,7 +497,15 @@ static int fpr_set_msa(struct task_struc
 	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,
@@ -505,6 +513,8 @@ static int fpr_set(struct task_struct *t
 {
 	int err;
 
+	BUG_ON(count % sizeof(elf_fpreg_t));
+
 	/* XXX fcr31  */
 
 	if (sizeof(target->thread.fpu.fpr[0]) == sizeof(elf_fpreg_t))



[Index of Archives]     [Linux Kernel]     [Kernel Development Newbies]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite Hiking]     [Linux Kernel]     [Linux SCSI]