path: root/kernel/bpf
diff options
authorAlexei Starovoitov <>2016-03-09 20:02:33 -0800
committerDavid S. Miller <>2016-03-09 23:27:30 -0500
commitcdc4e47da8f4c32eeb6b2061a8a834f4362a12b7 (patch)
treed66e39c8dccee7e5cf1662305a102c6235d315be /kernel/bpf
parentb8cdc05173f05d212627b7aba7ec47fa334a79f2 (diff)
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: ffeedafbf023 ("bpf: introduce current->pid, tgid, uid, gid, comm accessors") Reported-by: Tobias Waldekranz <> Signed-off-by: Alexei Starovoitov <> Signed-off-by: David S. Miller <>
Diffstat (limited to 'kernel/bpf')
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 4504ca66118d..50da680c479f 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -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;