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gfs2: Fix use-after-free in gfs2_logd after withdraw 

When the gfs2_logd daemon withdrew, the withdraw sequence called
into make_fs_ro() to make the file system read-only. That caused the
journal descriptors to be freed. However, those journal descriptors
were used by gfs2_logd's call to gfs2_ail_flush_reqd(). This caused
a use-after free and NULL pointer dereference.

This patch changes function gfs2_logd() so that it stops all logd
work until the thread is told to stop. Once a withdraw is done,
it only does an interruptible sleep.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
This commit is contained in:
Bob Peterson 2020-04-24 12:17:33 -05:00 committed by Andreas Gruenbacher
parent 53af80ce0e
commit d22f69a08d
1 changed files with 5 additions and 0 deletions
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5
fs/gfs2/log.c
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@ -1131,6 +1131,10 @@ int gfs2_logd(void *data)
while (!kthread_should_stop()) {
if (gfs2_withdrawn(sdp)) {
msleep_interruptible(HZ);
continue;
}
/* Check for errors writing to the journal */
if (sdp->sd_log_error) {
gfs2_lm(sdp,
@ -1139,6 +1143,7 @@ int gfs2_logd(void *data)
"prevent further damage.\n",
sdp->sd_fsname, sdp->sd_log_error);
gfs2_withdraw(sdp);
continue;
}
did_flush = false;