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author | Ilya Dryomov <idryomov@gmail.com> | 2015-11-02 17:13:58 +0100 |
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committer | Ilya Dryomov <idryomov@gmail.com> | 2015-11-02 23:37:46 +0100 |
commit | 583d0fef756a7615e50f0f68ea0892a497d03971 (patch) | |
tree | 6064fa517086baae5daa12f683d9af51d4be9ed4 /drivers | |
parent | a51983e4dd2d4d63912aab939f657c4cd476e21a (diff) | |
download | linux-583d0fef756a7615e50f0f68ea0892a497d03971.tar.bz2 |
libceph: clear msg->con in ceph_msg_release() only
The following bit in ceph_msg_revoke_incoming() is unsafe:
struct ceph_connection *con = msg->con;
if (!con)
return;
mutex_lock(&con->mutex);
<more msg->con use>
There is nothing preventing con from getting destroyed right after
msg->con test. One easy way to reproduce this is to disable message
signing only on the server side and try to map an image. The system
will go into a
libceph: read_partial_message ffff880073f0ab68 signature check failed
libceph: osd0 192.168.255.155:6801 bad crc/signature
libceph: read_partial_message ffff880073f0ab68 signature check failed
libceph: osd0 192.168.255.155:6801 bad crc/signature
loop which has to be interrupted with Ctrl-C. Hit Ctrl-C and you are
likely to end up with a random GP fault if the reset handler executes
"within" ceph_msg_revoke_incoming():
<yet another reply w/o a signature>
...
<Ctrl-C>
rbd_obj_request_end
ceph_osdc_cancel_request
__unregister_request
ceph_osdc_put_request
ceph_msg_revoke_incoming
...
osd_reset
__kick_osd_requests
__reset_osd
remove_osd
ceph_con_close
reset_connection
<clear con->in_msg->con>
<put con ref>
put_osd
<free osd/con>
<msg->con use> <-- !!!
If ceph_msg_revoke_incoming() executes "before" the reset handler,
osd/con will be leaked because ceph_msg_revoke_incoming() clears
con->in_msg but doesn't put con ref, while reset_connection() only puts
con ref if con->in_msg != NULL.
The current msg->con scheme was introduced by commits 38941f8031bf
("libceph: have messages point to their connection") and 92ce034b5a74
("libceph: have messages take a connection reference"), which defined
when messages get associated with a connection and when that
association goes away. Part of the problem is that this association is
supposed to go away in much too many places; closing this race entirely
requires either a rework of the existing or an addition of a new layer
of synchronization.
In lieu of that, we can make it *much* less likely to hit by
disassociating messages only on their destruction and resend through
a different connection. This makes the code simpler and is probably
a good thing to do regardless - this patch adds a msg_con_set() helper
which is is called from only three places: ceph_con_send() and
ceph_con_in_msg_alloc() to set msg->con and ceph_msg_release() to clear
it.
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Diffstat (limited to 'drivers')
0 files changed, 0 insertions, 0 deletions