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From: Ard Biesheuvel <ardb@kernel.org>
To: linux-efi@vger.kernel.org
Cc: oleksandr@natalenko.name, jk@ozlabs.org, mjg59@google.com,
	David.Laight@aculab.com, Ard Biesheuvel <ardb@kernel.org>,
	Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@gmail.com>
Subject: [PATCH] efivarfs: revert "fix memory leak in efivarfs_create()"
Date: Wed, 25 Nov 2020 08:53:03 +0100
Message-ID: <20201125075303.3963-1-ardb@kernel.org> (raw)

The memory leak addressed by commit fe5186cf12e3 is a false positive:
all allocations are recorded in a linked list, and freed when the
filesystem is unmounted. This leads to double frees, and as reported
by David, leads to crashes if SLUB is configured to self destruct when
double frees occur.

So drop the redundant kfree() again, and instead, mark the offending
pointer variable so the allocation is ignored by kmemleak.

Cc: Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@gmail.com>
Fixes: fe5186cf12e3 ("efivarfs: fix memory leak in efivarfs_create()")
Reported-by: David Laight <David.Laight@aculab.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 fs/efivarfs/inode.c | 1 +
 fs/efivarfs/super.c | 1 -
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/efivarfs/inode.c b/fs/efivarfs/inode.c
index 96c0c86f3fff..38324427a2b3 100644
--- a/fs/efivarfs/inode.c
+++ b/fs/efivarfs/inode.c
@@ -103,6 +103,7 @@ static int efivarfs_create(struct inode *dir, struct dentry *dentry,
 	var->var.VariableName[i] = '\0';
 
 	inode->i_private = var;
+	kmemleak_ignore(var);
 
 	err = efivar_entry_add(var, &efivarfs_list);
 	if (err)
diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c
index f943fd0b0699..15880a68faad 100644
--- a/fs/efivarfs/super.c
+++ b/fs/efivarfs/super.c
@@ -21,7 +21,6 @@ LIST_HEAD(efivarfs_list);
 static void efivarfs_evict_inode(struct inode *inode)
 {
 	clear_inode(inode);
-	kfree(inode->i_private);
 }
 
 static const struct super_operations efivarfs_ops = {
-- 
2.17.1


             reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-25  7:53 Ard Biesheuvel [this message]
2020-11-25  8:05 ` Oleksandr Natalenko
2020-11-25  8:05   ` Ard Biesheuvel
2020-11-25  8:25     ` Greg Kroah-Hartman
2020-11-25 10:27 ` Oleksandr Natalenko
2020-11-25 10:28   ` Ard Biesheuvel
2020-11-27 16:50     ` Jonathon Fernyhough
2020-11-27 16:58       ` Ard Biesheuvel
2020-11-27 16:59       ` Oleksandr Natalenko

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