linux-kernel - [tip: efi/urgent] efivarfs: revert "fix memory leak in efivarfs

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Message-ID: <160649576599.3364.9419789594382396613.tip-bot2@tip-bot2>
Date:   Fri, 27 Nov 2020 16:49:25 -0000
From:   "tip-bot2 for Ard Biesheuvel" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Vamshi K Sthambamkadi <vamshi.k.sthambamkadi@...il.com>,
        David Laight <David.Laight@...lab.com>,
        Ard Biesheuvel <ardb@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: efi/urgent] efivarfs: revert "fix memory leak in efivarfs_create()"

The following commit has been merged into the efi/urgent branch of tip:

Commit-ID:     ff04f3b6f2e27f8ae28a498416af2a8dd5072b43
Gitweb:        https://git.kernel.org/tip/ff04f3b6f2e27f8ae28a498416af2a8dd5072b43
Author:        Ard Biesheuvel <ardb@...nel.org>
AuthorDate:    Wed, 25 Nov 2020 08:45:55 +01:00
Committer:     Ard Biesheuvel <ardb@...nel.org>
CommitterDate: Wed, 25 Nov 2020 16:55:02 +01:00

efivarfs: revert "fix memory leak in efivarfs_create()"

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@...il.com>
Fixes: fe5186cf12e3 ("efivarfs: fix memory leak in efivarfs_create()")
Reported-by: David Laight <David.Laight@...lab.com>
Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 fs/efivarfs/inode.c | 2 ++
 fs/efivarfs/super.c | 1 -
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/efivarfs/inode.c b/fs/efivarfs/inode.c
index 96c0c86..0297ad9 100644
--- a/fs/efivarfs/inode.c
+++ b/fs/efivarfs/inode.c
@@ -7,6 +7,7 @@
 #include <linux/efi.h>
 #include <linux/fs.h>
 #include <linux/ctype.h>
+#include <linux/kmemleak.h>
 #include <linux/slab.h>
 #include <linux/uuid.h>
 
@@ -103,6 +104,7 @@ 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 f943fd0..15880a6 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 = {