mm: don't allow oversized kvmalloc() calls

'kvmalloc()' is a convenience function for people who want to do a
kmalloc() but fall back on vmalloc() if there aren't enough physically
contiguous pages, or if the allocation is larger than what kmalloc()
supports.

However, let's make sure it doesn't get _too_ easy to do crazy things
with it.  In particular, don't allow big allocations that could be due
to integer overflow or underflow.  So make sure the allocation size fits
in an 'int', to protect against trivial integer conversion issues.

Acked-by: Willy Tarreau <w@1wt.eu>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/util.c b/mm/util.c
index db3091116b7c250a44caa614335a7de644e5f495..499b6b5767ed11955ed40fce7b75bcc87e23c09f 100644 (file)
--- a/mm/util.c
+++ b/mm/util.c
@@ -593,6 +593,10 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
        if (ret || size <= PAGE_SIZE)
                return ret;
 
+       /* Don't even allow crazy sizes */
+       if (WARN_ON_ONCE(size > INT_MAX))
+               return NULL;
+
        return __vmalloc_node(size, 1, flags, node,
                        __builtin_return_address(0));
 }