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authorDavid Teigland <teigland@redhat.com>2009-06-18 22:20:24 +0400
committerDavid Teigland <teigland@redhat.com>2009-06-18 22:42:42 +0400
commitc78a87d0a1fc885dfdbe21fd5e07787691dfb068 (patch)
tree73f6056f87cd9183e04f3b9f6a4245876cf0cb23 /fs/dlm/plock.c
parenta566a6b11c86147fe9fc9db7ab15f9eecca3e862 (diff)
downloadlinux-c78a87d0a1fc885dfdbe21fd5e07787691dfb068.tar.xz
dlm: fix plock use-after-free
Fix a regression from the original addition of nfs lock support 586759f03e2e9031ac5589912a51a909ed53c30a. When a synchronous (non-nfs) plock completes, the waiting thread will wake up and free the op struct. This races with the user thread in dev_write() which goes on to read the op's callback field to check if the lock is async and needs a callback. This check can happen on the freed op. The fix is to note the callback value before the op can be freed. Signed-off-by: David Teigland <teigland@redhat.com>
Diffstat (limited to 'fs/dlm/plock.c')
-rw-r--r--fs/dlm/plock.c17
1 files changed, 10 insertions, 7 deletions
diff --git a/fs/dlm/plock.c b/fs/dlm/plock.c
index 894a32d438d5..16f682e26c07 100644
--- a/fs/dlm/plock.c
+++ b/fs/dlm/plock.c
@@ -353,7 +353,7 @@ static ssize_t dev_write(struct file *file, const char __user *u, size_t count,
{
struct dlm_plock_info info;
struct plock_op *op;
- int found = 0;
+ int found = 0, do_callback = 0;
if (count != sizeof(info))
return -EINVAL;
@@ -366,21 +366,24 @@ static ssize_t dev_write(struct file *file, const char __user *u, size_t count,
spin_lock(&ops_lock);
list_for_each_entry(op, &recv_list, list) {
- if (op->info.fsid == info.fsid && op->info.number == info.number &&
+ if (op->info.fsid == info.fsid &&
+ op->info.number == info.number &&
op->info.owner == info.owner) {
+ struct plock_xop *xop = (struct plock_xop *)op;
list_del_init(&op->list);
- found = 1;
- op->done = 1;
memcpy(&op->info, &info, sizeof(info));
+ if (xop->callback)
+ do_callback = 1;
+ else
+ op->done = 1;
+ found = 1;
break;
}
}
spin_unlock(&ops_lock);
if (found) {
- struct plock_xop *xop;
- xop = (struct plock_xop *)op;
- if (xop->callback)
+ if (do_callback)
dlm_plock_callback(op);
else
wake_up(&recv_wq);