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control_if: Avoid heap-use-after-free in osmo_wqueue_bfd_cb 

Imagine following scenario:
1- client connects to CTRL iface, a new conn is created with POLL_READ
enabled.
2- A non-related event happens which triggers a TRAP to be sent. As a
result, the wqueue for the conn has now enabled POLL_WRITE, and message
will be sent next time we go through osmo_main_select().
3- At the same time, we receive the GET cmd from the CTRL client, which
means POLL_READ event will be also triggered next time we call
osmo_main_select().
4- osmo_main_select triggers osmo_wqueue_bfd_cb with both READ/WRITE
flags set.
5- The read_cb of wqueue is executed first. The handler closes the CTRL
conn for some reason, freeing the osmo_fd struct and returns.
6- osmo_qeueue_bfd_cb keeps using the already freed osmo_fd and calls
write_cb.

So in step 6 we get a heap-use-after-free catched by AddressSanitizer:

20180424135406115 DLCTRL <0018> control_if.c:506 accept()ed new CTRL connection from (r=10.42.42.1:53910<->l=10.42.42.7:4249)
20180424135406116 DLCTRL <0018> control_cmd.c:378 Command: GET bts.0.oml-connection-state
20180424135406117 DLINP <0013> bts_ipaccess_nanobts.c:417 Identified BTS 1/0/0
20180424135406118 DNM <0005> abis_nm.c:1628 Get Attr (bts=0)
20180424135406118 DNM <0005> abis_nm.c:1628 Get Attr (bts=0)
20180424135406118 DCTRL <000e> osmo_bsc_ctrl.c:158 BTS connection (re)established, sending TRAP.
20180424135406119 DLCTRL <0018> control_if.c:173 close()d CTRL connection (r=10.42.42.1:53910<->l=10.42.42.7:4249)
=================================================================
==12301==ERROR: AddressSanitizer: heap-use-after-free on address 0x611000003e04 at pc 0x7f23091c3a2f bp 0x7ffc0cb73ff0 sp 0x7ffc0cb73fe8
READ of size 4 at 0x611000003e04 thread T0
    #0 0x7f23091c3a2e in osmo_wqueue_bfd_cb /home/osmocom-build/jenkins/workspace/osmo-gsm-tester_build-osmo-bsc/libosmocore/src/write_queue.c:65
    #1 0x7f23091ad5d8 in osmo_fd_disp_fds /home/osmocom-build/jenkins/workspace/osmo-gsm-tester_build-osmo-bsc/libosmocore/src/select.c:216
    #2 0x7f23091ad5d8 in osmo_select_main /home/osmocom-build/jenkins/workspace/osmo-gsm-tester_build-osmo-bsc/libosmocore/src/select.c:256
    #3 0x56538bdb7a26 in main /home/osmocom-build/jenkins/workspace/osmo-gsm-tester_build-osmo-bsc/osmo-bsc/src/osmo-bsc/osmo_bsc_main.c:532
    #4 0x7f23077532e0 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x202e0)
    #5 0x56538bdb8999 in _start (/home/jenkins/workspace/osmo-gsm-tester_run-prod/trial-896/inst/osmo-bsc/bin/osmo-bsc+0x259999)

Fixes: OS#3206

Change-Id: I84d10caaadcfa6bd46ba8756ca89aa0badcfd2e3
This commit is contained in:
Pau Espin 2018-05-04 18:20:35 +02:00
parent 13154ffabd
commit 686eba9bfc
2 changed files with 25 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/osmocom/core/write_queue.h
View File

@ -42,11 +42,11 @@ struct osmo_wqueue {
/*! actual linked list implementing the queue */
struct llist_head msg_queue;
/*! call-back in case qeueue is readable */
/*! call-back in case qeueue is readable. Return -EBADF if fd is freed inside cb. */
int (*read_cb)(struct osmo_fd *fd);
/*! call-back in case qeueue is writable */
/*! call-back in case qeueue is writable. Return -EBADF if fd is freed inside cb. */
int (*write_cb)(struct osmo_fd *fd, struct msgb *msg);
/*! call-back in case qeueue has exceptions */
/*! call-back in case qeueue has exceptions. Return -EBADF if fd is freed inside cb. */
int (*except_cb)(struct osmo_fd *fd);
};

41
src/ctrl/control_if.c
View File

@ -327,7 +327,7 @@ err:
static int handle_control_read(struct osmo_fd * bfd)
{
int ret = -1;
int ret;
struct osmo_wqueue *queue;
struct ctrl_connection *ccon;
struct msgb *msg = NULL;
@ -337,27 +337,28 @@ static int handle_control_read(struct osmo_fd * bfd)
ccon = container_of(queue, struct ctrl_connection, write_queue);
ret = ipa_msg_recv_buffered(bfd->fd, &msg, &ccon->pending_msg);
if (ret <= 0) {
if (ret == -EAGAIN)
/* received part of a message, it is stored in ccon->pending_msg and there's
* nothing left to do now. */
return 0;
if (ret == 0) {
/* msg was already discarded. */
if (ret == 0) {
control_close_conn(ccon);
ret = -EIO;
}
else
LOGP(DLCTRL, LOGL_ERROR, "Failed to parse ip access message: %d\n", ret);
return ret;
goto close_fd;
} else if (ret == -EAGAIN) {
/* received part of a message, it is stored in ccon->pending_msg and there's
* nothing left to do now. */
return 0;
} else if (ret < 0) {
LOGP(DLCTRL, LOGL_ERROR, "Failed to parse ip access message: %d\n", ret);
return 0;
}
ret = ctrl_handle_msg(ctrl, ccon, msg);
msgb_free(msg);
if (ret)
control_close_conn(ccon);
return ret;
goto close_fd;
return 0;
close_fd:
control_close_conn(ccon);
return -EBADF;
}
int ctrl_handle_msg(struct ctrl_handle *ctrl, struct ctrl_connection *ccon, struct msgb *msg)
@ -435,12 +436,14 @@ static int control_write_cb(struct osmo_fd *bfd, struct msgb *msg)
ccon = container_of(queue, struct ctrl_connection, write_queue);
rc = write(bfd->fd, msg->data, msg->len);
if (rc == 0)
if (rc == 0) {
control_close_conn(ccon);
else if (rc != msg->len)
return -EBADF;
}
if (rc != msg->len)
LOGP(DLCTRL, LOGL_ERROR, "Failed to write message to the CTRL connection.\n");
return rc;
return 0;
}
/*! Allocate CTRL connection