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VFS: fix a race in lease-breaking during truncate

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It is possible that another process could acquire a new file lease right
after break_lease() is called during a truncate, but before lease-granting
is disabled by the subsequent get_write_access().  Merely switching the
order of the break_lease() and get_write_access() calls prevents this race.

Signed-off-by: David M. Richter <[email protected]>
Signed-off-by: "J. Bruce Fields" <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
david m. richter 2007-07-31 00:39:12 -07:00 • committed by Linus Torvalds
commit 9700382c3c
1 changed files with 9 additions and 7 deletions
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18
fs/open.c
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@ -256,24 +256,26 @@ static long do_sys_truncate(const char __user * path, loff_t length)
if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
goto dput_and_out;
/*
* Make sure that there are no leases.
*/
error = break_lease(inode, FMODE_WRITE);
if (error)
goto dput_and_out;
error = get_write_access(inode);
if (error)
goto dput_and_out;
/*
* Make sure that there are no leases. get_write_access() protects
* against the truncate racing with a lease-granting setlease().
*/
error = break_lease(inode, FMODE_WRITE);
if (error)
goto put_write_and_out;
error = locks_verify_truncate(inode, NULL, length);
if (!error) {
DQUOT_INIT(inode);
error = do_truncate(nd.dentry, length, 0, NULL);
}
put_write_access(inode);
put_write_and_out:
put_write_access(inode);
dput_and_out:
path_release(&nd);
out: