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selftests/bpf: adjust dummy_st_ops_success to detect additional error
stable inclusion from stable-v6.6.39 commit 264451a364dba5ca6cb2878126a9798dfc0b1a06 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IAD6H2 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=264451a364dba5ca6cb2878126a9798dfc0b1a06 -------------------------------- [ Upstream commit 3b3b84aacb4420226576c9732e7b539ca7b79633 ] As reported by Jose E. Marchesi in off-list discussion, GCC and LLVM generate slightly different code for dummy_st_ops_success/test_1(): SEC("struct_ops/test_1") int BPF_PROG(test_1, struct bpf_dummy_ops_state *state) { int ret; if (!state) return 0xf2f3f4f5; ret = state->val; state->val = 0x5a; return ret; } GCC-generated LLVM-generated ---------------------------- --------------------------- 0: r1 = *(u64 *)(r1 + 0x0) 0: w0 = -0xd0c0b0b 1: if r1 == 0x0 goto 5f 1: r1 = *(u64 *)(r1 + 0x0) 2: r0 = *(s32 *)(r1 + 0x0) 2: if r1 == 0x0 goto 6f 3: *(u32 *)(r1 + 0x0) = 0x5a 3: r0 = *(u32 *)(r1 + 0x0) 4: exit 4: w2 = 0x5a 5: r0 = -0xd0c0b0b 5: *(u32 *)(r1 + 0x0) = r2 6: exit 6: exit If the 'state' argument is not marked as nullable in net/bpf/bpf_dummy_struct_ops.c, the verifier would assume that 'r1 == 0x0' is never true: - for the GCC version, this means that instructions #5-6 would be marked as dead and removed; - for the LLVM version, all instructions would be marked as live. The test dummy_st_ops/dummy_init_ret_value actually sets the 'state' parameter to NULL. Therefore, when the 'state' argument is not marked as nullable, the GCC-generated version of the code would trigger a NULL pointer dereference at instruction #3. This patch updates the test_1() test case to always follow a shape similar to the GCC-generated version above, in order to verify whether the 'state' nullability is marked correctly. Reported-by:Jose E. Marchesi <jemarch@gnu.org> Signed-off-by: