This is a note to let you know that I've just added the patch titled bpf: avoid copying junk bytes in bpf_get_current_comm() to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: bpf-avoid-copying-junk-bytes-in-bpf_get_current_comm.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Sat Apr 16 10:02:53 PDT 2016 From: Alexei Starovoitov <ast@xxxxxx> Date: Wed, 9 Mar 2016 20:02:33 -0800 Subject: bpf: avoid copying junk bytes in bpf_get_current_comm() From: Alexei Starovoitov <ast@xxxxxx> [ Upstream commit cdc4e47da8f4c32eeb6b2061a8a834f4362a12b7 ] 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 <tobias@xxxxxxxxxxxxxx> Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/bpf/helpers.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -166,7 +166,7 @@ static u64 bpf_get_current_comm(u64 r1, 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; } Patches currently in stable-queue which might be from ast@xxxxxx are queue-4.4/bpf-avoid-copying-junk-bytes-in-bpf_get_current_comm.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html