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Date: Fri, 6 Jan 2017 13:32:39 -0800
From: Kees Cook <keescook@...omium.org>
To: James Morris <james.l.morris@...cle.com>
Cc: linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org,
Mathias Svensson <idolf@...gle.com>,
Stephen Röttger <sroettger@...gle.com>,
Will Drewry <drewry@...gle.com>
Subject: [PATCH] samples/seccomp: fix 64-bit comparison macros
There were some bugs in the JNE64 and JLT64 comparision macros. This fixes
them, improves comments, and cleans up the file while we are at it.
Reported-by: Stephen Röttger <sroettger@...gle.com>
Signed-off-by: Mathias Svensson <idolf@...gle.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
Cc: stable@...r.kernel.org
---
James, can you apply this to your -next tree please?
---
samples/seccomp/bpf-helper.h | 125 +++++++++++++++++++++++++------------------
1 file changed, 72 insertions(+), 53 deletions(-)
diff --git a/samples/seccomp/bpf-helper.h b/samples/seccomp/bpf-helper.h
index 38ee70f3cd5b..1d8de9edd858 100644
--- a/samples/seccomp/bpf-helper.h
+++ b/samples/seccomp/bpf-helper.h
@@ -138,7 +138,7 @@ union arg64 {
#define ARG_32(idx) \
BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx))
-/* Loads hi into A and lo in X */
+/* Loads lo into M[0] and hi into M[1] and A */
#define ARG_64(idx) \
BPF_STMT(BPF_LD+BPF_W+BPF_ABS, LO_ARG(idx)), \
BPF_STMT(BPF_ST, 0), /* lo -> M[0] */ \
@@ -153,88 +153,107 @@ union arg64 {
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (value), 1, 0), \
jt
-/* Checks the lo, then swaps to check the hi. A=lo,X=hi */
+#define JA32(value, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (value), 0, 1), \
+ jt
+
+#define JGE32(value, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 0, 1), \
+ jt
+
+#define JGT32(value, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 0, 1), \
+ jt
+
+#define JLE32(value, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 1, 0), \
+ jt
+
+#define JLT32(value, jt) \
+ BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 1, 0), \
+ jt
+
+/*
+ * All the JXX64 checks assume lo is saved in M[0] and hi is saved in both
+ * A and M[1]. This invariant is kept by restoring A if necessary.
+ */
#define JEQ64(lo, hi, jt) \
+ /* if (hi != arg.hi) goto NOMATCH; */ \
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+ /* if (lo != arg.lo) goto NOMATCH; */ \
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 0, 2), \
- BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+ BPF_STMT(BPF_LD+BPF_MEM, 1), \
jt, \
- BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+ BPF_STMT(BPF_LD+BPF_MEM, 1)
#define JNE64(lo, hi, jt) \
- BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 5, 0), \
- BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+ /* if (hi != arg.hi) goto MATCH; */ \
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 3), \
+ BPF_STMT(BPF_LD+BPF_MEM, 0), \
+ /* if (lo != arg.lo) goto MATCH; */ \
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (lo), 2, 0), \
- BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+ BPF_STMT(BPF_LD+BPF_MEM, 1), \
jt, \
- BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
-
-#define JA32(value, jt) \
- BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (value), 0, 1), \
- jt
+ BPF_STMT(BPF_LD+BPF_MEM, 1)
#define JA64(lo, hi, jt) \
+ /* if (hi & arg.hi) goto MATCH; */ \
BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (hi), 3, 0), \
- BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+ BPF_STMT(BPF_LD+BPF_MEM, 0), \
+ /* if (lo & arg.lo) goto MATCH; */ \
BPF_JUMP(BPF_JMP+BPF_JSET+BPF_K, (lo), 0, 2), \
- BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+ BPF_STMT(BPF_LD+BPF_MEM, 1), \
jt, \
- BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+ BPF_STMT(BPF_LD+BPF_MEM, 1)
-#define JGE32(value, jt) \
- BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 0, 1), \
- jt
-
-#define JLT32(value, jt) \
- BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (value), 1, 0), \
- jt
-
-/* Shortcut checking if hi > arg.hi. */
#define JGE64(lo, hi, jt) \
+ /* if (hi > arg.hi) goto MATCH; */ \
BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \
+ /* if (hi != arg.hi) goto NOMATCH; */ \
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
- BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+ BPF_STMT(BPF_LD+BPF_MEM, 0), \
+ /* if (lo >= arg.lo) goto MATCH; */ \
BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (lo), 0, 2), \
- BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
- jt, \
- BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
-
-#define JLT64(lo, hi, jt) \
- BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \
- BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
- BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
- BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \
- BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+ BPF_STMT(BPF_LD+BPF_MEM, 1), \
jt, \
- BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+ BPF_STMT(BPF_LD+BPF_MEM, 1)
-#define JGT32(value, jt) \
- BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 0, 1), \
- jt
-
-#define JLE32(value, jt) \
- BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (value), 1, 0), \
- jt
-
-/* Check hi > args.hi first, then do the GE checking */
#define JGT64(lo, hi, jt) \
+ /* if (hi > arg.hi) goto MATCH; */ \
BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 4, 0), \
+ /* if (hi != arg.hi) goto NOMATCH; */ \
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
- BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+ BPF_STMT(BPF_LD+BPF_MEM, 0), \
+ /* if (lo > arg.lo) goto MATCH; */ \
BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 0, 2), \
- BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+ BPF_STMT(BPF_LD+BPF_MEM, 1), \
jt, \
- BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+ BPF_STMT(BPF_LD+BPF_MEM, 1)
#define JLE64(lo, hi, jt) \
- BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (hi), 6, 0), \
- BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 3), \
- BPF_STMT(BPF_LD+BPF_MEM, 0), /* swap in lo */ \
+ /* if (hi < arg.hi) goto MATCH; */ \
+ BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \
+ /* if (hi != arg.hi) goto NOMATCH; */ \
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
+ BPF_STMT(BPF_LD+BPF_MEM, 0), \
+ /* if (lo <= arg.lo) goto MATCH; */ \
BPF_JUMP(BPF_JMP+BPF_JGT+BPF_K, (lo), 2, 0), \
- BPF_STMT(BPF_LD+BPF_MEM, 1), /* passed: swap hi back in */ \
+ BPF_STMT(BPF_LD+BPF_MEM, 1), \
+ jt, \
+ BPF_STMT(BPF_LD+BPF_MEM, 1)
+
+#define JLT64(lo, hi, jt) \
+ /* if (hi < arg.hi) goto MATCH; */ \
+ BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (hi), 0, 4), \
+ /* if (hi != arg.hi) goto NOMATCH; */ \
+ BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, (hi), 0, 5), \
+ BPF_STMT(BPF_LD+BPF_MEM, 0), \
+ /* if (lo < arg.lo) goto MATCH; */ \
+ BPF_JUMP(BPF_JMP+BPF_JGE+BPF_K, (lo), 2, 0), \
+ BPF_STMT(BPF_LD+BPF_MEM, 1), \
jt, \
- BPF_STMT(BPF_LD+BPF_MEM, 1) /* failed: swap hi back in */
+ BPF_STMT(BPF_LD+BPF_MEM, 1)
#define LOAD_SYSCALL_NR \
BPF_STMT(BPF_LD+BPF_W+BPF_ABS, \
--
2.7.4
--
Kees Cook
Nexus Security
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