xtensa: prevent arbitrary read in ptrace

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

[akpm@linux-foundation.org: s/EIO/EFAULT/]
Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
Cc: Christian Zankel <chris@zankel.net>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/xtensa/kernel/ptrace.c b/arch/xtensa/kernel/ptrace.c
index c72c9473ef99..a0d042aa2967 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 -EFAULT;
+
 #if XTENSA_HAVE_COPROCESSORS
         /* Flush all coprocessors before we overwrite them. */
         coprocessor_flush_all(ti);