Re: [PATCH v2 4/4] samples: Add example of using PTRACE_GETFD in conjunction with user trap
flat view
From: Oleg Nesterov <oleg@redhat.com>
Date: 2019-12-09 19:30:11
Also in:
linux-fsdevel, lkml
On 12/09, Sargun Dhillon wrote:
+#define CHILD_PORT_TRY_BIND 80 +#define CHILD_PORT_ACTUAL_BIND 4998
...
quoted hunk ↗ jump to hunk
+static int handle_req(int listener) +{ + struct sockaddr_in addr = { + .sin_family = AF_INET, + .sin_port = htons(4998),
then I think .sin_port = htons(CHILD_PORT_ACTUAL_BIND); would be more clear...
quoted hunk ↗ jump to hunk
+ .sin_addr = { + .s_addr = htonl(INADDR_LOOPBACK) + } + }; + struct ptrace_getfd_args getfd_args = { + .options = PTRACE_GETFD_O_CLOEXEC + }; + struct seccomp_notif_sizes sizes; + struct seccomp_notif_resp *resp; + struct seccomp_notif *req; + int fd, ret = 1; + + if (seccomp(SECCOMP_GET_NOTIF_SIZES, 0, &sizes) < 0) { + perror("seccomp(GET_NOTIF_SIZES)"); + goto out; + } + req = malloc(sizes.seccomp_notif); + if (!req) + goto out; + memset(req, 0, sizeof(*req)); + + resp = malloc(sizes.seccomp_notif_resp); + if (!resp) + goto out_free_req; + memset(resp, 0, sizeof(*resp)); + + if (ioctl(listener, SECCOMP_IOCTL_NOTIF_RECV, req)) { + perror("ioctl recv"); + goto out; + } + printf("Child tried to call bind with fd: %lld\n", req->data.args[0]); + getfd_args.fd = req->data.args[0]; + fd = ptrace_getfd(req->pid, &getfd_args);
and iiuc otherwise you do not need to ptrace the child. So you could remove ptrace(PTRACE_SEIZE) in main() and just do ptrace(PTRACE_SEIZE, req->pid); fd = ptrace_getfd(req->pid, &getfd_args); ptrace(PTRACE_DETACH, req->pid); here. However, PTRACE_DETACH won't work, it needs the stopped tracee. We can add PTRACE_DETACH_ASYNC, but this makes me think that PTRACE_GETFD has nothing to do with ptrace. May be a new syscall which does ptrace_may_access() + get_task_file() will make more sense? Oleg.