提交 cdc4e47d 编写于 作者: A Alexei Starovoitov 提交者: David S. Miller

bpf: avoid copying junk bytes in bpf_get_current_comm()

Lots of places in the kernel use memcpy(buf, comm, TASK_COMM_LEN); but
the result is typically passed to print("%s", buf) and extra bytes
after zero don't cause any harm.
In bpf the result of bpf_get_current_comm() is used as the part of
map key and was causing spurious hash map mismatches.
Use strlcpy() to guarantee zero-terminated string.
bpf verifier checks that output buffer is zero-initialized,
so even for short task names the output buffer don't have junk bytes.
Note it's not a security concern, since kprobe+bpf is root only.

Fixes: ffeedafb ("bpf: introduce current->pid, tgid, uid, gid, comm accessors")
Reported-by: NTobias Waldekranz <tobias@waldekranz.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
上级 b8cdc051
......@@ -166,7 +166,7 @@ static u64 bpf_get_current_comm(u64 r1, u64 size, u64 r3, u64 r4, u64 r5)
if (!task)
return -EINVAL;
memcpy(buf, task->comm, min_t(size_t, size, sizeof(task->comm)));
strlcpy(buf, task->comm, min_t(size_t, size, sizeof(task->comm)));
return 0;
}
......
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