selftests/bpf: Add tests for unaligned syscall ctx accesses

Add coverage for unaligned access with fixed offsets and variable
offsets, and through helpers or kfuncs.

Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260406194403.1649608-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 133 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/verifier_ctx.c b/tools/testing/selftests/bpf/progs/verifier_ctx.c
index 6e683dd8002a..887cd07ed885 100644
--- a/tools/testing/selftests/bpf/progs/verifier_ctx.c
+++ b/tools/testing/selftests/bpf/progs/verifier_ctx.c
@@ -321,6 +321,30 @@ int syscall_ctx_fixed_off_read(void *ctx)
 }
 
 SEC("?syscall")
+__description("syscall: unaligned read ctx with fixed offset")
+__success
+int syscall_ctx_unaligned_fixed_off_read(void *ctx)
+{
+	char *p = ctx;
+	volatile __u32 val;
+
+	val = *(__u32 *)(p + 2);
+	(void)val;
+	return 0;
+}
+
+SEC("?syscall")
+__description("syscall: unaligned write ctx with fixed offset")
+__success
+int syscall_ctx_unaligned_fixed_off_write(void *ctx)
+{
+	char *p = ctx;
+
+	*(__u32 *)(p + 2) = 0;
+	return 0;
+}
+
+SEC("?syscall")
 __description("syscall: read ctx with variable offset")
 __success
 int syscall_ctx_var_off_read(void *ctx)
@@ -351,6 +375,38 @@ int syscall_ctx_var_off_write(void *ctx)
 }
 
 SEC("?syscall")
+__description("syscall: unaligned read ctx with variable offset")
+__success
+int syscall_ctx_unaligned_var_off_read(void *ctx)
+{
+	__u64 off = bpf_get_prandom_u32();
+	char *p = ctx;
+	volatile __u32 val;
+
+	off &= 0xfc;
+	off += 2;
+	p += off;
+	val = *(__u32 *)p;
+	(void)val;
+	return 0;
+}
+
+SEC("?syscall")
+__description("syscall: unaligned write ctx with variable offset")
+__success
+int syscall_ctx_unaligned_var_off_write(void *ctx)
+{
+	__u64 off = bpf_get_prandom_u32();
+	char *p = ctx;
+
+	off &= 0xfc;
+	off += 2;
+	p += off;
+	*(__u32 *)p = 0;
+	return 0;
+}
+
+SEC("?syscall")
 __description("syscall: reject negative variable offset ctx access")
 __failure __msg("min value is negative")
 int syscall_ctx_neg_var_off(void *ctx)
@@ -399,6 +455,28 @@ int syscall_ctx_helper_fixed_off_write(void *ctx)
 }
 
 SEC("?syscall")
+__description("syscall: helper unaligned read ctx with fixed offset")
+__success
+int syscall_ctx_helper_unaligned_fixed_off_read(void *ctx)
+{
+	char *p = ctx;
+
+	p += 2;
+	return bpf_strncmp(p, 4, ctx_strncmp_target);
+}
+
+SEC("?syscall")
+__description("syscall: helper unaligned write ctx with fixed offset")
+__success
+int syscall_ctx_helper_unaligned_fixed_off_write(void *ctx)
+{
+	char *p = ctx;
+
+	p += 2;
+	return bpf_probe_read_kernel(p, 4, 0);
+}
+
+SEC("?syscall")
 __description("syscall: helper read ctx with variable offset")
 __success
 int syscall_ctx_helper_var_off_read(void *ctx)
@@ -425,6 +503,34 @@ int syscall_ctx_helper_var_off_write(void *ctx)
 }
 
 SEC("?syscall")
+__description("syscall: helper unaligned read ctx with variable offset")
+__success
+int syscall_ctx_helper_unaligned_var_off_read(void *ctx)
+{
+	__u64 off = bpf_get_prandom_u32();
+	char *p = ctx;
+
+	off &= 0xfc;
+	off += 2;
+	p += off;
+	return bpf_strncmp(p, 4, ctx_strncmp_target);
+}
+
+SEC("?syscall")
+__description("syscall: helper unaligned write ctx with variable offset")
+__success
+int syscall_ctx_helper_unaligned_var_off_write(void *ctx)
+{
+	__u64 off = bpf_get_prandom_u32();
+	char *p = ctx;
+
+	off &= 0xfc;
+	off += 2;
+	p += off;
+	return bpf_probe_read_kernel(p, 4, 0);
+}
+
+SEC("?syscall")
 __description("syscall: helper read zero-sized ctx access")
 __success
 int syscall_ctx_helper_zero_sized_read(void *ctx)
@@ -467,6 +573,33 @@ int syscall_ctx_kfunc_var_off(void *ctx)
 }
 
 SEC("?syscall")
+__description("syscall: kfunc unaligned access ctx with fixed offset")
+__success
+int syscall_ctx_kfunc_unaligned_fixed_off(void *ctx)
+{
+	char *p = ctx;
+
+	p += 2;
+	bpf_kfunc_call_test_mem_len_pass1(p, 4);
+	return 0;
+}
+
+SEC("?syscall")
+__description("syscall: kfunc unaligned access ctx with variable offset")
+__success
+int syscall_ctx_kfunc_unaligned_var_off(void *ctx)
+{
+	__u64 off = bpf_get_prandom_u32();
+	char *p = ctx;
+
+	off &= 0xfc;
+	off += 2;
+	p += off;
+	bpf_kfunc_call_test_mem_len_pass1(p, 4);
+	return 0;
+}
+
+SEC("?syscall")
 __description("syscall: kfunc access zero-sized ctx")
 __success
 int syscall_ctx_kfunc_zero_sized(void *ctx)