[PATCH 3.15 038/109] net: filter: fix upper BPF instruction limit

[Greg Kroah-Hartman]

3.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Kees Cook <keescook@xxxxxxxxxxxx>

[ Upstream commit 6f9a093b66ce7cacc110d8737c03686e80ecfda6 ]

The original checks (via sk_chk_filter) for instruction count uses ">",
not ">=", so changing this in sk_convert_filter has the potential to break
existing seccomp filters that used exactly BPF_MAXINSNS many instructions.

Fixes: bd4cf0ed331a ("net: filter: rework/optimize internal BPF interpreter's instruction set")
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v3.15+
Acked-by: Daniel Borkmann <dborkman@xxxxxxxxxx>
Acked-by: Alexei Starovoitov <ast@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/core/filter.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -872,7 +872,7 @@ int sk_convert_filter(struct sock_filter
 	BUILD_BUG_ON(BPF_MEMWORDS * sizeof(u32) > MAX_BPF_STACK);
 	BUILD_BUG_ON(FP_REG + 1 != MAX_BPF_REG);
 
-	if (len <= 0 || len >= BPF_MAXINSNS)
+	if (len <= 0 || len > BPF_MAXINSNS)
 		return -EINVAL;
 
 	if (new_prog) {


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