mm: don't allow oversized kvmalloc() calls

commit 7661809d493b426e979f39ab512e3adf41fbcc69 upstream.

'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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/mm/util.c b/mm/util.c
index c18202b3e659d2f2ab97988c7569d68906cb6bd2..8bd4a20262a91b405a206890d18c52b1da514f2d 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));
 }