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: Christian Zankel <chris@zankel.net>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/xtensa/kernel/ptrace.c b/arch/xtensa/kernel/ptrace.c
index c72c9473ef9913f9666ff54f869fe35fdfd27509..ddce75efd74c665ce23668fece31798cf511716a 100644 (file)
--- 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);