On 10/16/2017 08:18 PM, Richard Weinberger wrote:
Sadly we cannot use get_task_comm() since bpf_get_current_comm()
allows truncation.
Signed-off-by: Richard Weinberger <rich...@nod.at>
---
kernel/bpf/helpers.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 511c9d522cfc..4b042b24524d 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -18,6 +18,7 @@
#include <linux/sched.h>
#include <linux/uidgid.h>
#include <linux/filter.h>
+#include <linux/sched/task.h>
/* If kernel subsystem is allowing eBPF programs to call this function,
* inside its own verifier_ops->get_func_proto() callback it should return
@@ -149,7 +150,9 @@ BPF_CALL_2(bpf_get_current_comm, char *, buf, u32, size)
{
struct task_struct *task = current;
+ task_lock(task);
strncpy(buf, task->comm, size);
+ task_unlock(task);
Wouldn't this potentially lead to a deadlock? E.g. you attach yourself
to task_lock() / spin_lock() / etc, and then the BPF prog triggers the
bpf_get_current_comm() taking the lock again ...
/* Verifier guarantees that size > 0. For task->comm exceeding
* size, guarantee that buf is %NUL-terminated. Unconditionally
