vfs: take f_lock on modifying f_mode after open time

We'll introduce FMODE_RANDOM which will be runtime modified. So protect all runtime modification to f_mode with f_lock to avoid races. Signed-off-by: Wu Fengguang <[email protected]> Cc: Al Viro <[email protected]> Cc: Christoph Hellwig <[email protected]> Cc: Trond Myklebust <[email protected]> Cc: Chuck Lever <[email protected]> Cc: <[email protected]> [2.6.33.x] Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
dabrace · Mar 6, 2010 · 42e4960 · 42e4960
1 parent 85f1fb7
commit 42e4960
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diff --git a/fs/file_table.c b/fs/file_table.c
@@ -393,7 +393,9 @@ void mark_files_ro(struct super_block *sb)
 			continue;
 		if (!(f->f_mode & FMODE_WRITE))
 			continue;
+		spin_lock(&f->f_lock);
 		f->f_mode &= ~FMODE_WRITE;
+		spin_unlock(&f->f_lock);
 		if (file_check_writeable(f) != 0)
 			continue;
 		file_release_write(f);

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
@@ -1998,7 +1998,9 @@ nfs4_file_downgrade(struct file *filp, unsigned int share_access)
 {
 	if (share_access & NFS4_SHARE_ACCESS_WRITE) {
 		drop_file_write_access(filp);
+		spin_lock(&filp->f_lock);
 		filp->f_mode = (filp->f_mode | FMODE_READ) & ~FMODE_WRITE;
+		spin_unlock(&filp->f_lock);
 	}
 }