When using error-injection function through bpf to change the return
code, we need to know if the function is sleepable or not.
Currently the code assumes that all error-inject functions are sleepable,
except for a few selected of them, hardcoded in kernel/bpf/verifier.c
Add a new flag to error-inject so we can code that information where the
function is declared.
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
---
new in v4:
- another approach would be to define a new kfunc_set, and register
it with btf. But in that case, what program type would we use?
BPF_PROG_TYPE_UNSPEC?
- also note that maybe we should consider all of the functions
non-sleepable and only mark some as sleepable. IMO it makes more
sense to be more restrictive by default.
---
include/asm-generic/error-injection.h | 1 +
kernel/bpf/verifier.c | 10 ++++++++--
lib/error-inject.c | 2 ++
3 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/include/asm-generic/error-injection.h b/include/asm-generic/error-injection.h
index fbca56bd9cbc..5974942353a6 100644
--- a/include/asm-generic/error-injection.h
+++ b/include/asm-generic/error-injection.h
@@ -9,6 +9,7 @@ enum {
EI_ETYPE_ERRNO, /* Return -ERRNO if failure */
EI_ETYPE_ERRNO_NULL, /* Return -ERRNO or NULL if failure */
EI_ETYPE_TRUE, /* Return true if failure */
+ EI_ETYPE_NS_ERRNO, /* Return -ERRNO if failure and tag the function as non-sleepable */
};
struct error_injection_entry {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 0f339f9058f3..45c8feea6478 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -14085,6 +14085,11 @@ static int check_non_sleepable_error_inject(u32 btf_id)
return btf_id_set_contains(&btf_non_sleepable_error_inject, btf_id);
}
+static int is_non_sleepable_error_inject(unsigned long addr)
+{
+ return get_injectable_error_type(addr) == EI_ETYPE_NS_ERRNO;
+}
+
int bpf_check_attach_target(struct bpf_verifier_log *log,
const struct bpf_prog *prog,
const struct bpf_prog *tgt_prog,
@@ -14281,8 +14286,9 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
/* fentry/fexit/fmod_ret progs can be sleepable only if they are
* attached to ALLOW_ERROR_INJECTION and are not in denylist.
*/
- if (!check_non_sleepable_error_inject(btf_id) &&
- within_error_injection_list(addr))
+ if (within_error_injection_list(addr) &&
+ !check_non_sleepable_error_inject(btf_id) &&
+ !is_non_sleepable_error_inject(addr))
ret = 0;
break;
case BPF_PROG_TYPE_LSM:
diff --git a/lib/error-inject.c b/lib/error-inject.c
index 2ff5ef689d72..560c3b18f439 100644
--- a/lib/error-inject.c
+++ b/lib/error-inject.c
@@ -183,6 +183,8 @@ static const char *error_type_string(int etype)
return "ERRNO_NULL";
case EI_ETYPE_TRUE:
return "TRUE";
+ case EI_ETYPE_NS_ERRNO:
+ return "NS_ERRNO";
default:
return "(unknown)";
}
--
2.35.1
