4.2.8-ckt7 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------ From: Alexei Starovoitov <[email protected]> commit cdc4e47da8f4c32eeb6b2061a8a834f4362a12b7 upstream. 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 <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Signed-off-by: David S. Miller <[email protected]> Signed-off-by: Kamal Mostafa <[email protected]> --- kernel/bpf/helpers.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 1447ec0..c2e2bad 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -171,7 +171,7 @@ 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; } -- 2.7.4
