[PATCH] xtensa: prevent arbitrary read in ptrace

[Dan Rosenberg <drosenberg@vsecurity.com>]

Prevent an arbitrary kernel read. Check the user pointer with
access_ok() before copying data in.

Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
Cc: stable@kernel.org
---
 arch/xtensa/kernel/ptrace.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/xtensa/kernel/ptrace.c b/arch/xtensa/kernel/ptrace.c
index c72c947..ddce75e 100644
--- a/arch/xtensa/kernel/ptrace.c
+++ b/arch/xtensa/kernel/ptrace.c
@@ -147,6 +147,9 @@ int ptrace_setxregs(struct task_struct *child, void __user *uregs)
 	elf_xtregs_t *xtregs = uregs;
 	int ret = 0;
 
+	if (!access_ok(VERIFY_READ, uregs, sizeof(elf_xtregs_t)))
+		return -EIO;
+
 #if XTENSA_HAVE_COPROCESSORS
 	/* Flush all coprocessors before we overwrite them. */
 	coprocessor_flush_all(ti);