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authorPavel Emelyanov <xemul@openvz.org>2007-09-20 12:45:02 +0400
committerJ. Bruce Fields <bfields@citi.umich.edu>2007-10-09 18:32:45 -0400
commit85c59580b30c82aa771aa33b37217a6b6851bc14 (patch)
tree02e96b437a63908ad3791021d352ad2aefff9936 /fs/locks.c
parentf0c1cd0eaf0b127356c2c09e40305453bc361b0f (diff)
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locks: Fix potential OOPS in generic_setlease()
This code is run under lock_kernel(), which is dropped during sleeping operations, so the following race is possible: CPU1: CPU2: vfs_setlease(); vfs_setlease(); lock_kernel(); lock_kernel(); /* spin */ generic_setlease(): ... for (before = ...) /* here we found some lease after * which we will insert the new one */ fl = locks_alloc_lock(); /* go to sleep in this allocation and * drop the BKL */ generic_setlease(): ... for (before = ...) /* here we find the "before" pointing * at the one we found on CPU1 */ ->fl_change(my_before, arg); lease_modify(); locks_free_lock(); /* and we freed it */ ... unlock_kernel(); locks_insert_lock(before, fl); /* OOPS! We have just tried to add the lease * at the tail of already removed one */ The similar races are already handled in other code - all the allocations are performed before any checks/updates. Thanks to Kamalesh Babulal for testing and for a bug report on an earlier version. Signed-off-by: Pavel Emelyanov <xemul@openvz.org> Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu> Cc: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Diffstat (limited to 'fs/locks.c')
-rw-r--r--fs/locks.c21
1 files changed, 12 insertions, 9 deletions
diff --git a/fs/locks.c b/fs/locks.c
index 282b6c11670a..43dbc7f566fa 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1343,6 +1343,7 @@ int fcntl_getlease(struct file *filp)
int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
{
struct file_lock *fl, **before, **my_before = NULL, *lease;
+ struct file_lock *new_fl = NULL;
struct dentry *dentry = filp->f_path.dentry;
struct inode *inode = dentry->d_inode;
int error, rdlease_count = 0, wrlease_count = 0;
@@ -1369,6 +1370,11 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
|| (atomic_read(&inode->i_count) > 1)))
goto out;
+ error = -ENOMEM;
+ new_fl = locks_alloc_lock();
+ if (new_fl == NULL)
+ goto out;
+
/*
* At this point, we know that if there is an exclusive
* lease on this file, then we hold it on this filp
@@ -1411,18 +1417,15 @@ int generic_setlease(struct file *filp, long arg, struct file_lock **flp)
if (!leases_enable)
goto out;
- error = -ENOMEM;
- fl = locks_alloc_lock();
- if (fl == NULL)
- goto out;
-
- locks_copy_lock(fl, lease);
+ locks_copy_lock(new_fl, lease);
+ locks_insert_lock(before, new_fl);
- locks_insert_lock(before, fl);
+ *flp = new_fl;
+ return 0;
- *flp = fl;
- error = 0;
out:
+ if (new_fl != NULL)
+ locks_free_lock(new_fl);
return error;
}
EXPORT_SYMBOL(generic_setlease);