CIFS: Do not permit write to a range mandatory locked with a read lock
We don't need to permit a write to the area locked with a read lock
by any process including the process that issues the write.
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <smfrench@gmail.com>
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index bceffa8..ebebbb2 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -759,10 +759,15 @@
}
}
+#define CIFS_LOCK_OP 0
+#define CIFS_READ_OP 1
+#define CIFS_WRITE_OP 2
+
+/* @rw_check : 0 - no op, 1 - read, 2 - write */
static bool
cifs_find_fid_lock_conflict(struct cifs_fid_locks *fdlocks, __u64 offset,
__u64 length, __u8 type, struct cifsFileInfo *cfile,
- struct cifsLockInfo **conf_lock, bool rw_check)
+ struct cifsLockInfo **conf_lock, int rw_check)
{
struct cifsLockInfo *li;
struct cifsFileInfo *cur_cfile = fdlocks->cfile;
@@ -772,9 +777,13 @@
if (offset + length <= li->offset ||
offset >= li->offset + li->length)
continue;
- if (rw_check && server->ops->compare_fids(cfile, cur_cfile) &&
- current->tgid == li->pid)
- continue;
+ if (rw_check != CIFS_LOCK_OP && current->tgid == li->pid &&
+ server->ops->compare_fids(cfile, cur_cfile)) {
+ /* shared lock prevents write op through the same fid */
+ if (!(li->type & server->vals->shared_lock_type) ||
+ rw_check != CIFS_WRITE_OP)
+ continue;
+ }
if ((type & server->vals->shared_lock_type) &&
((server->ops->compare_fids(cfile, cur_cfile) &&
current->tgid == li->pid) || type == li->type))
@@ -789,7 +798,7 @@
bool
cifs_find_lock_conflict(struct cifsFileInfo *cfile, __u64 offset, __u64 length,
__u8 type, struct cifsLockInfo **conf_lock,
- bool rw_check)
+ int rw_check)
{
bool rc = false;
struct cifs_fid_locks *cur;
@@ -825,7 +834,7 @@
down_read(&cinode->lock_sem);
exist = cifs_find_lock_conflict(cfile, offset, length, type,
- &conf_lock, false);
+ &conf_lock, CIFS_LOCK_OP);
if (exist) {
flock->fl_start = conf_lock->offset;
flock->fl_end = conf_lock->offset + conf_lock->length - 1;
@@ -872,7 +881,7 @@
down_write(&cinode->lock_sem);
exist = cifs_find_lock_conflict(cfile, lock->offset, lock->length,
- lock->type, &conf_lock, false);
+ lock->type, &conf_lock, CIFS_LOCK_OP);
if (!exist && cinode->can_cache_brlcks) {
list_add_tail(&lock->llist, &cfile->llist->locks);
up_write(&cinode->lock_sem);
@@ -2466,7 +2475,7 @@
down_read(&cinode->lock_sem);
if (!cifs_find_lock_conflict(cfile, pos, iov_length(iov, nr_segs),
server->vals->exclusive_lock_type, NULL,
- true)) {
+ CIFS_WRITE_OP)) {
mutex_lock(&inode->i_mutex);
rc = __generic_file_aio_write(iocb, iov, nr_segs,
&iocb->ki_pos);
@@ -2901,7 +2910,7 @@
down_read(&cinode->lock_sem);
if (!cifs_find_lock_conflict(cfile, pos, iov_length(iov, nr_segs),
tcon->ses->server->vals->shared_lock_type,
- NULL, true))
+ NULL, CIFS_READ_OP))
rc = generic_file_aio_read(iocb, iov, nr_segs, pos);
up_read(&cinode->lock_sem);
return rc;