diff mbox series

[v2,bpf-next,2/4] bpf: Teach the verifier to recognize rdonly_mem as not null.

Message ID 20230321203854.3035-3-alexei.starovoitov@gmail.com (mailing list archive)
State Accepted
Commit 1057d299459657b85e593a4b6294a000f920672a
Delegated to: BPF
Headers show
Series bpf: Support ksym detection in light skeleton. | expand

Checks

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bpf/vmtest-bpf-next-VM_Test-32 success Logs for test_verifier on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-33 success Logs for test_verifier on aarch64 with llvm-16
bpf/vmtest-bpf-next-VM_Test-34 success Logs for test_verifier on s390x with gcc
bpf/vmtest-bpf-next-VM_Test-35 success Logs for test_verifier on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-36 success Logs for test_verifier on x86_64 with llvm-16
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 28 this patch: 28
netdev/cc_maintainers warning 8 maintainers not CCed: song@kernel.org sdf@google.com haoluo@google.com yhs@fb.com john.fastabend@gmail.com kpsingh@kernel.org jolsa@kernel.org martin.lau@linux.dev
netdev/build_clang success Errors and warnings before: 18 this patch: 18
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 28 this patch: 28
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 28 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-next-VM_Test-10 success Logs for test_maps on aarch64 with llvm-16
bpf/vmtest-bpf-next-VM_Test-14 success Logs for test_progs on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-15 success Logs for test_progs on aarch64 with llvm-16
bpf/vmtest-bpf-next-VM_Test-17 success Logs for test_progs on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-18 success Logs for test_progs on x86_64 with llvm-16
bpf/vmtest-bpf-next-VM_Test-19 success Logs for test_progs_no_alu32 on aarch64 with gcc
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Commit Message

Alexei Starovoitov March 21, 2023, 8:38 p.m. UTC 
From: Alexei Starovoitov <ast@kernel.org>

Teach the verifier to recognize PTR_TO_MEM | MEM_RDONLY as not NULL
otherwise if (!bpf_ksym_exists(known_kfunc)) doesn't go through
dead code elimination.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 kernel/bpf/verifier.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

Comments

David Vernet March 21, 2023, 10:21 p.m. UTC | #1 
On Tue, Mar 21, 2023 at 01:38:52PM -0700, Alexei Starovoitov wrote:
> From: Alexei Starovoitov <ast@kernel.org>
> 
> Teach the verifier to recognize PTR_TO_MEM | MEM_RDONLY as not NULL
> otherwise if (!bpf_ksym_exists(known_kfunc)) doesn't go through
> dead code elimination.
> 
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Acked-by: David Vernet <void@manifault.com>
diff mbox series

Patch

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 8bc44f5dc5b6..5693e4a92752 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -486,8 +486,17 @@  static bool type_is_sk_pointer(enum bpf_reg_type type)
 		type == PTR_TO_XDP_SOCK;
 }
 
+static bool type_may_be_null(u32 type)
+{
+	return type & PTR_MAYBE_NULL;
+}
+
 static bool reg_type_not_null(enum bpf_reg_type type)
 {
+	if (type_may_be_null(type))
+		return false;
+
+	type = base_type(type);
 	return type == PTR_TO_SOCKET ||
 		type == PTR_TO_TCP_SOCK ||
 		type == PTR_TO_MAP_VALUE ||
@@ -531,11 +540,6 @@  static bool type_is_rdonly_mem(u32 type)
 	return type & MEM_RDONLY;
 }
 
-static bool type_may_be_null(u32 type)
-{
-	return type & PTR_MAYBE_NULL;
-}
-
 static bool is_acquire_function(enum bpf_func_id func_id,
 				const struct bpf_map *map)
 {