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bpf: Handle bpf_mprog_query with NULL entry

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Improve consistency for bpf_mprog_query() API and let the latter also handle
a NULL entry as can be the case for tcx. Instead of returning -ENOENT, we
copy a count of 0 and revision of 1 to user space, so that this can be fed
into a subsequent bpf_mprog_attach() call as expected_revision. A BPF self-
test as part of this series has been added to assert this case.

Suggested-by: Lorenz Bauer <lmb@isovalent.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20231006220655.1653-2-daniel@iogearbox.net
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
This commit is contained in:
Daniel Borkmann 2023-10-07 00:06:50 +02:00 committed by Martin KaFai Lau
parent a4fe78386a
commit edfa9af0a7
2 changed files with 7 additions and 11 deletions
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10
kernel/bpf/mprog.c
View File

@ -401,14 +401,16 @@ int bpf_mprog_query(const union bpf_attr *attr, union bpf_attr __user *uattr,
struct bpf_mprog_cp *cp;
struct bpf_prog *prog;
const u32 flags = 0;
u32 id, count = 0;
u64 revision = 1;
int i, ret = 0;
u32 id, count;
u64 revision;
if (attr->query.query_flags || attr->query.attach_flags)
return -EINVAL;
revision = bpf_mprog_revision(entry);
count = bpf_mprog_total(entry);
if (entry) {
revision = bpf_mprog_revision(entry);
count = bpf_mprog_total(entry);
}
if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags)))
return -EFAULT;
if (copy_to_user(&uattr->query.revision, &revision, sizeof(revision)))

8
kernel/bpf/tcx.c
View File

@ -123,7 +123,6 @@ int tcx_prog_query(const union bpf_attr *attr, union bpf_attr __user *uattr)
{
bool ingress = attr->query.attach_type == BPF_TCX_INGRESS;
struct net *net = current->nsproxy->net_ns;
struct bpf_mprog_entry *entry;
struct net_device *dev;
int ret;
@ -133,12 +132,7 @@ int tcx_prog_query(const union bpf_attr *attr, union bpf_attr __user *uattr)
ret = -ENODEV;
goto out;
}
entry = tcx_entry_fetch(dev, ingress);
if (!entry) {
ret = -ENOENT;
goto out;
}
ret = bpf_mprog_query(attr, uattr, entry);
ret = bpf_mprog_query(attr, uattr, tcx_entry_fetch(dev, ingress));
out:
rtnl_unlock();
return ret;