laforge has submitted this change. ( https://gerrit.osmocom.org/c/libosmocore/+/35982?usp=email )
Change subject: osmo_io_uring: Detach msghdr from iofd before calling iofd_handle_send_completion() ......................................................................
osmo_io_uring: Detach msghdr from iofd before calling iofd_handle_send_completion()
msghdr must be detached, because subsequent callback at iofd_handle_send_completion() may destroy the iofd (which in turn frees this msghdr, if still attached) and frees the msghdr, causing a double free.
Related: OS#5751 Change-Id: Ia349f73de2145fa360b20dd40deb73a8ffc71f07 --- M src/core/osmo_io_uring.c 1 file changed, 24 insertions(+), 1 deletion(-)
Approvals: Jenkins Builder: Verified laforge: Looks good to me, but someone else must approve pespin: Looks good to me, approved
diff --git a/src/core/osmo_io_uring.c b/src/core/osmo_io_uring.c index 3812b50..cb636da 100644 --- a/src/core/osmo_io_uring.c +++ b/src/core/osmo_io_uring.c @@ -195,6 +195,15 @@ { struct osmo_io_fd *iofd = msghdr->iofd;
+ /* Detach msghdr from iofd. It might get freed here or it is freed during iofd_handle_send_completion(). + * If there is pending data to send, iofd_uring_submit_tx() will attach it again. + * iofd_handle_send_completion() will invoke a callback function to signal the possibility of write/send. + * This callback function might close iofd, leading to the potential freeing of iofd->u.uring.write_msghdr if + * still attached. Since iofd_handle_send_completion() frees msghdr at the end of the function, detaching + * msghdr here prevents a double-free bug. */ + if (iofd->u.uring.write_msghdr == msghdr) + iofd->u.uring.write_msghdr = NULL; + if (OSMO_UNLIKELY(IOFD_FLAG_ISSET(iofd, IOFD_FLAG_CLOSED))) { msgb_free(msghdr->msg); iofd_msghdr_free(msghdr); @@ -202,7 +211,6 @@ iofd_handle_send_completion(iofd, rc, msghdr); }
- iofd->u.uring.write_msghdr = NULL; /* submit the next to-be-transmitted message for this file descriptor */ if (iofd->u.uring.write_enabled && !IOFD_FLAG_ISSET(iofd, IOFD_FLAG_CLOSED)) iofd_uring_submit_tx(iofd);