linux-kernel - [PATCH] afs: Fix storage of cell names

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Date:   Wed, 24 Jun 2020 17:00:24 +0100
From:   David Howells <dhowells@...hat.com>
To:     torvalds@...ux-foundation.org
Cc:     Colin Ian King <colin.king@...onical.com>, dhowells@...hat.com,
        linux-afs@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] afs: Fix storage of cell names

The cell name stored in the afs_cell struct is a 64-char + NUL buffer -
when it needs to be able to handle up to AFS_MAXCELLNAME (256 chars) + NUL.

Fix this by changing the array to a pointer and allocating the string.

Found using Coverity.

Fixes: 989782dcdc91 ("afs: Overhaul cell database management")
Reported-by: Colin Ian King <colin.king@...onical.com>
Signed-off-by: David Howells <dhowells@...hat.com>
---

 fs/afs/cell.c     |    9 +++++++++
 fs/afs/internal.h |    2 +-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/fs/afs/cell.c b/fs/afs/cell.c
index 0d25565a2e37..1cdabbdeeb2c 100644
--- a/fs/afs/cell.c
+++ b/fs/afs/cell.c
@@ -154,10 +154,17 @@ static struct afs_cell *afs_alloc_cell(struct afs_net *net,
 		return ERR_PTR(-ENOMEM);
 	}
 
+	cell->name = kmalloc(namelen + 1, GFP_KERNEL);
+	if (!cell->name) {
+		kfree(cell);
+		return ERR_PTR(-ENOMEM);
+	}
+
 	cell->net = net;
 	cell->name_len = namelen;
 	for (i = 0; i < namelen; i++)
 		cell->name[i] = tolower(name[i]);
+	cell->name[i] = 0;
 
 	atomic_set(&cell->usage, 2);
 	INIT_WORK(&cell->manager, afs_manage_cell);
@@ -207,6 +214,7 @@ static struct afs_cell *afs_alloc_cell(struct afs_net *net,
 	if (ret == -EINVAL)
 		printk(KERN_ERR "kAFS: bad VL server IP address\n");
 error:
+	kfree(cell->name);
 	kfree(cell);
 	_leave(" = %d", ret);
 	return ERR_PTR(ret);
@@ -489,6 +497,7 @@ static void afs_cell_destroy(struct rcu_head *rcu)
 	afs_put_vlserverlist(cell->net, rcu_access_pointer(cell->vl_servers));
 	afs_put_cell(cell->net, cell->alias_of);
 	key_put(cell->anonymous_key);
+	kfree(cell->name);
 	kfree(cell);
 
 	_leave(" [destroyed]");
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 5892605b1a44..bf26fd28ccbd 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -390,7 +390,7 @@ struct afs_cell {
 	struct afs_vlserver_list __rcu *vl_servers;
 
 	u8			name_len;	/* Length of name */
-	char			name[64 + 1];	/* Cell name, case-flattened and NUL-padded */
+	char			*name;		/* Cell name, case-flattened and NUL-padded */
 };
 
 /*