Commit bcbfd0c0 authored by Eric Dumazet's avatar Eric Dumazet Committed by Greg Kroah-Hartman

net: filter: fix possible use after free

[ No appicable upstream commit, this bug has been subsequently been
  fixed as a side effect of other changes. ]

If kmemdup() fails, we free fp->orig_prog and return -ENOMEM

sk_attach_filter()
 -> sk_filter_uncharge(sk, fp)
  -> sk_filter_release(fp)
   -> call_rcu(&fp->rcu, sk_filter_release_rcu)
    -> sk_filter_release_rcu()
     -> sk_release_orig_filter()
        fprog = fp->orig_prog; // not NULL, but points to freed memory
	  kfree(fprog->filter); // use after free, potential corruption
          kfree(fprog); // double free or corruption

Note: This was fixed in 3.17+ with commit 278571ba
("net: filter: simplify socket charging")

Found by AddressSanitizer
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Fixes: a3ea269b ("net: filter: keep original BPF program around")
Acked-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
Acked-by: default avatarDaniel Borkmann <dborkman@redhat.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e39b8b0e
...@@ -1318,6 +1318,7 @@ static int sk_store_orig_filter(struct sk_filter *fp, ...@@ -1318,6 +1318,7 @@ static int sk_store_orig_filter(struct sk_filter *fp,
fkprog->filter = kmemdup(fp->insns, fsize, GFP_KERNEL); fkprog->filter = kmemdup(fp->insns, fsize, GFP_KERNEL);
if (!fkprog->filter) { if (!fkprog->filter) {
kfree(fp->orig_prog); kfree(fp->orig_prog);
fp->orig_prog = NULL;
return -ENOMEM; return -ENOMEM;
} }
......
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