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: [<ffffffff8112e8dc>] 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:
[<ffffffff8112ea52>] do_kern_mount+0x52/0x130
[<ffffffff811497ff>] do_mount+0x2bf/0x810
[<ffffffff810face3>] ? strndup_user+0x53/0x70
[<ffffffff81149de0>] sys_mount+0x90/0xe0
[<ffffffff81002fdb>] 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 <joro@xxxxxxxxxx>
---
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
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