linux-kernel - [PATCH AUTOSEL 6.8 09/25] fs/9p: fix uninitialized values during inode evict

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Date: Sun,  7 Apr 2024 09:10:57 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Eric Van Hensbergen <ericvh@...nel.org>,
	syzbot+eb83fe1cce5833cd66a0@...kaller.appspotmail.com,
	Sasha Levin <sashal@...nel.org>,
	lucho@...kov.net,
	asmadeus@...ewreck.org,
	v9fs@...ts.linux.dev
Subject: [PATCH AUTOSEL 6.8 09/25] fs/9p: fix uninitialized values during inode evict

From: Eric Van Hensbergen <ericvh@...nel.org>

[ Upstream commit 6630036b7c228f57c7893ee0403e92c2db2cd21d ]

If an iget fails due to not being able to retrieve information
from the server then the inode structure is only partially
initialized.  When the inode gets evicted, references to
uninitialized structures (like fscache cookies) were being
made.

This patch checks for a bad_inode before doing anything other
than clearing the inode from the cache.  Since the inode is
bad, it shouldn't have any state associated with it that needs
to be written back (and there really isn't a way to complete
those anyways).

Reported-by: syzbot+eb83fe1cce5833cd66a0@...kaller.appspotmail.com
Signed-off-by: Eric Van Hensbergen <ericvh@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/9p/vfs_inode.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 32572982f72e6..7d42f0c6c644f 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -371,17 +371,21 @@ void v9fs_evict_inode(struct inode *inode)
 	struct v9fs_inode __maybe_unused *v9inode = V9FS_I(inode);
 	__le32 __maybe_unused version;
 
-	truncate_inode_pages_final(&inode->i_data);
+	if (!is_bad_inode(inode)) {
+		truncate_inode_pages_final(&inode->i_data);
 
-	version = cpu_to_le32(v9inode->qid.version);
-	netfs_clear_inode_writeback(inode, &version);
+		version = cpu_to_le32(v9inode->qid.version);
+		netfs_clear_inode_writeback(inode, &version);
 
-	clear_inode(inode);
-	filemap_fdatawrite(&inode->i_data);
+		clear_inode(inode);
+		filemap_fdatawrite(&inode->i_data);
 
 #ifdef CONFIG_9P_FSCACHE
-	fscache_relinquish_cookie(v9fs_inode_cookie(v9inode), false);
+		if (v9fs_inode_cookie(v9inode))
+			fscache_relinquish_cookie(v9fs_inode_cookie(v9inode), false);
 #endif
+	} else
+		clear_inode(inode);
 }
 
 static int v9fs_test_inode(struct inode *inode, void *data)
-- 
2.43.0