From: Joerg Roedel Subject: [PATCH] ext4: Fix 'return 0' for error case in ext4_fill_super Date: Thu, 18 Nov 2010 22:47:12 +0100 Message-ID: <1290116832-29443-1-git-send-email-joro@8bytes.org> Cc: linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, Joerg Roedel To: Theodore Ts'o , Andreas Dilger Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org The ext4_fill_super may return with value 0 in case of an error. The reason is that the ret variable is used to store the return value of a called function and is not set back to an error value later on. This issue caused a NULL pointer de-ref in vfs_kern_mount on one of my machines when it tried to mount a partition: BUG: unable to handle kernel NULL pointer dereference at 0000000000000090 IP: [] vfs_kern_mount+0x7c/0x180 PGD 218480067 PUD 225323067 PMD 0 Oops: 0000 [#1] SMP last sysfs file: /sys/devices/system/cpu/cpu5/cache/index2/shared_cpu_map CPU 1 ... Process mount (pid: 3591, threadinfo ffff8802258fc000, task ffff88022586dac0) Stack: ffff8802258fde38 0000000000000000 ffff880225e299b0 ffff880200000001 ffffffff81a230e0 ffff880225e2c818 ffff8802258fde88 ffffffff8112ea52 ffff8802258fde98 0000000000000246 ffff88022586dac0 0000000000000060 Call Trace: [] do_kern_mount+0x52/0x130 [] do_mount+0x2bf/0x810 [] ? strndup_user+0x53/0x70 [] sys_mount+0x90/0xe0 [] system_call_fastpath+0x16/0x1b This patch fixes the issue by using the 'err' variable instead of 'ret' for that function-call like it is done in for all other function-calls in ext4_fill_super too. If have seen this issue on 2.6.36 too, so this patch may be -stable material as well. Signed-off-by: Joerg Roedel --- fs/ext4/super.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 61182fe..499cf5d 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -3268,9 +3268,9 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) * Test whether we have more sectors than will fit in sector_t, * and whether the max offset is addressable by the page cache. */ - ret = generic_check_addressable(sb->s_blocksize_bits, + err = generic_check_addressable(sb->s_blocksize_bits, ext4_blocks_count(es)); - if (ret) { + if (err) { ext4_msg(sb, KERN_ERR, "filesystem" " too large to mount safely on this system"); if (sizeof(sector_t) < 8) -- 1.7.0.4