linux-kernel - [PATCH] AFS: Stop readlink() on AFS crashing because file not passed to afs

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Date:	Thu, 27 Aug 2009 13:22:31 +0100
From:	David Howells <dhowells@...hat.com>
To:	torvalds@...l.org, akpm@...ux-foundation.org
Cc:	linux-afs@...ts.infradead.org, linux-kernel@...r.kernel.org,
	David Howells <dhowells@...hat.com>,
	Anton Blanchard <anton@...ba.org>
Subject: [PATCH] AFS: Stop readlink() on AFS crashing because file not passed
	to afs_readpage()

kAFS crashes when asked to read a symbolic link because page_getlink() passes a
NULL file pointer to read_mapping_page(), but afs_readpage() expects a file
pointer from which to extract a key.

Modify afs_readpage() to request the appropriate key from the calling process's
keyrings if a file struct is not supplied with one attached.

Signed-off-by: David Howells <dhowells@...hat.com>
Acked-by: Anton Blanchard <anton@...ba.org>
---

 fs/afs/file.c |   18 +++++++++++++++---
 1 files changed, 15 insertions(+), 3 deletions(-)


diff --git a/fs/afs/file.c b/fs/afs/file.c
index 0149dab..681c2a7 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -134,9 +134,16 @@ static int afs_readpage(struct file *file, struct page *page)
 
 	inode = page->mapping->host;
 
-	ASSERT(file != NULL);
-	key = file->private_data;
-	ASSERT(key != NULL);
+	if (file) {
+		key = file->private_data;
+		ASSERT(key != NULL);
+	} else {
+		key = afs_request_key(AFS_FS_S(inode->i_sb)->volume->cell);
+		if (IS_ERR(key)) {
+			ret = PTR_ERR(key);
+			goto error_nokey;
+		}
+	}
 
 	_enter("{%x},{%lu},{%lu}", key_serial(key), inode->i_ino, page->index);
 
@@ -207,12 +214,17 @@ static int afs_readpage(struct file *file, struct page *page)
 		unlock_page(page);
 	}
 
+	if (!file)
+		key_put(key);
 	_leave(" = 0");
 	return 0;
 
 error:
 	SetPageError(page);
 	unlock_page(page);
+	if (!file)
+		key_put(key);
+error_nokey:
 	_leave(" = %d", ret);
 	return ret;
 }

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