Merge branch 'bpf: Allow reads from uninit stack'

Merge commit bf9bec4cb3a4 ("Merge branch 'bpf: Allow reads from uninit stack'")
from bpf-next to bpf tree to address verification issues in some programs
due to stack usage.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2 files changed, 91 insertions, 4 deletions

diff --git a/tools/testing/selftests/bpf/progs/test_global_func10.c b/tools/testing/selftests/bpf/progs/test_global_func10.c
index 98327bdbbfd2..8fba3f3649e2 100644
--- a/tools/testing/selftests/bpf/progs/test_global_func10.c
+++ b/tools/testing/selftests/bpf/progs/test_global_func10.c
@@ -5,12 +5,12 @@
 #include "bpf_misc.h"
 
 struct Small {
-	int x;
+	long x;
 };
 
 struct Big {
-	int x;
-	int y;
+	long x;
+	long y;
 };
 
 __noinline int foo(const struct Big *big)
@@ -22,7 +22,7 @@ __noinline int foo(const struct Big *big)
 }
 
 SEC("cgroup_skb/ingress")
-__failure __msg("invalid indirect read from stack")
+__failure __msg("invalid indirect access to stack")
 int global_func10(struct __sk_buff *skb)
 {
 	const struct Small small = {.x = skb->len };
diff --git a/tools/testing/selftests/bpf/progs/uninit_stack.c b/tools/testing/selftests/bpf/progs/uninit_stack.c
new file mode 100644
index 000000000000..8a403470e557
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/uninit_stack.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+/* Read an uninitialized value from stack at a fixed offset */
+SEC("socket")
+__naked int read_uninit_stack_fixed_off(void *ctx)
+{
+	asm volatile ("					\
+		r0 = 0;					\
+		/* force stack depth to be 128 */	\
+		*(u64*)(r10 - 128) = r1;		\
+		r1 = *(u8 *)(r10 - 8 );			\
+		r0 += r1;				\
+		r1 = *(u8 *)(r10 - 11);			\
+		r1 = *(u8 *)(r10 - 13);			\
+		r1 = *(u8 *)(r10 - 15);			\
+		r1 = *(u16*)(r10 - 16);			\
+		r1 = *(u32*)(r10 - 32);			\
+		r1 = *(u64*)(r10 - 64);			\
+		/* read from a spill of a wrong size, it is a separate	\
+		 * branch in check_stack_read_fixed_off()		\
+		 */					\
+		*(u32*)(r10 - 72) = r1;			\
+		r1 = *(u64*)(r10 - 72);			\
+		r0 = 0;					\
+		exit;					\
+"
+		      ::: __clobber_all);
+}
+
+/* Read an uninitialized value from stack at a variable offset */
+SEC("socket")
+__naked int read_uninit_stack_var_off(void *ctx)
+{
+	asm volatile ("					\
+		call %[bpf_get_prandom_u32];		\
+		/* force stack depth to be 64 */	\
+		*(u64*)(r10 - 64) = r0;			\
+		r0 = -r0;				\
+		/* give r0 a range [-31, -1] */		\
+		if r0 s<= -32 goto exit_%=;		\
+		if r0 s>= 0 goto exit_%=;		\
+		/* access stack using r0 */		\
+		r1 = r10;				\
+		r1 += r0;				\
+		r2 = *(u8*)(r1 + 0);			\
+exit_%=:	r0 = 0;					\
+		exit;					\
+"
+		      :
+		      : __imm(bpf_get_prandom_u32)
+		      : __clobber_all);
+}
+
+static __noinline void dummy(void) {}
+
+/* Pass a pointer to uninitialized stack memory to a helper.
+ * Passed memory block should be marked as STACK_MISC after helper call.
+ */
+SEC("socket")
+__log_level(7) __msg("fp-104=mmmmmmmm")
+__naked int helper_uninit_to_misc(void *ctx)
+{
+	asm volatile ("					\
+		/* force stack depth to be 128 */	\
+		*(u64*)(r10 - 128) = r1;		\
+		r1 = r10;				\
+		r1 += -128;				\
+		r2 = 32;				\
+		call %[bpf_trace_printk];		\
+		/* Call to dummy() forces print_verifier_state(..., true),	\
+		 * thus showing the stack state, matched by __msg().		\
+		 */					\
+		call %[dummy];				\
+		r0 = 0;					\
+		exit;					\
+"
+		      :
+		      : __imm(bpf_trace_printk),
+			__imm(dummy)
+		      : __clobber_all);
+}
+
+char _license[] SEC("license") = "GPL";