On 4/25/21 12:16 AM, Pedro Tammela wrote:
The 'bpf()' syscall is leaking the ENOTSUPP errno that is internal to the kernel[1].
More recent code is already using the correct EOPNOTSUPP, but changing
older return codes is not possible due to dependency concerns, so handle ENOTSUPP
in libbpf_strerror().
[1] https://lore.kernel.org/netdev/20200511165319.2251678-1-kuba@xxxxxxxxxx/
Signed-off-by: Pedro Tammela <pctammela@xxxxxxxxxxxx>
---
tools/lib/bpf/libbpf_errno.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/tools/lib/bpf/libbpf_errno.c b/tools/lib/bpf/libbpf_errno.c
index 0afb51f7a919..7de8bbc34a37 100644
--- a/tools/lib/bpf/libbpf_errno.c
+++ b/tools/lib/bpf/libbpf_errno.c
@@ -13,6 +13,9 @@
#include "libbpf.h"
+/* This errno is internal to the kernel but leaks in the bpf() syscall. */
+#define ENOTSUPP 524
+
/* make sure libbpf doesn't use kernel-only integer typedefs */
#pragma GCC poison u8 u16 u32 u64 s8 s16 s32 s64
@@ -43,6 +46,12 @@ int libbpf_strerror(int err, char *buf, size_t size)
err = err > 0 ? err : -err;
+ if (err == ENOTSUPP) {
+ snprintf(buf, size, "Operation not supported");
+ buf[size - 1] = '\0';
+ return 0;
+ }
+
if (err < __LIBBPF_ERRNO__START) {
int ret;
Could you fold this into the __LIBBPF_ERRNO__START test body to denote that it
belongs outside the libbpf error range? For example, could be simplified like this:
if (err < __LIBBPF_ERRNO__START) {
int ret;
/* Handle ENOTSUPP separate here given it's kernel internal,
* but for sake of error string it has the same meaning as
* the EOPNOTSUPP error.
*/
if (err == ENOTSUPP)
err = EOPNOTSUPP;
ret = strerror_r(err, buf, size);
buf[size - 1] = '\0';
return ret;
}
Thanks,
Daniel
