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Date: Thu, 17 Jan 2008 12:17:36 +0530
From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To: Mingming Cao <cmm@...ibm.com>
Cc: Valerie Clement <valerie.clement@...l.net>,
linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] Fix oops in mballoc caused by a variable overflow
On Wed, Jan 16, 2008 at 10:48:27AM -0800, Mingming Cao wrote:
> On Wed, 2008-01-16 at 20:11 +0100, Valerie Clement wrote:
> > A simple dd oopses the kernel (2.6.24-rc7 with the latest patch queue):
> > dd if=/dev/zero of=/mnt/test/foo bs=1M count=8096
> >
> > EXT4-fs: mballoc enabled
> > ------------[ cut here ]------------
> > kernel BUG at fs/ext4/mballoc.c:3148!
> >
> > The BUG_ON is:
> > BUG_ON(size <= 0 || size >= EXT4_BLOCKS_PER_GROUP(ac->ac_sb));
> >
> > where the value of "size" is 4293920768.
> >
> > This is due to the overflow of the variable "start" in the
> > ext4_mb_normalize_request() function.
> > The patch below fixes it.
> >
> Thanks!
>
> > Signed-off-by: Valerie Clement <valerie.clement@...l.net>
> > ---
> >
> > mballoc.c | 23 ++++++++++++-----------
> > 1 file changed, 12 insertions(+), 11 deletions(-)
> >
> >
> > Index: linux-2.6.24-rc7/fs/ext4/mballoc.c
> > ===================================================================
> > --- linux-2.6.24-rc7.orig/fs/ext4/mballoc.c 2008-01-16 19:22:45.000000000 +0100
> > +++ linux-2.6.24-rc7/fs/ext4/mballoc.c 2008-01-16 19:25:04.000000000 +0100
> > @@ -2990,6 +2990,7 @@ static void ext4_mb_normalize_request(st
> > struct list_head *cur;
> > loff_t size, orig_size;
> > ext4_lblk_t start, orig_start;
> > + ext4_fsblk_t pstart;
>
> ext4_fsblk_t is used for fs physical block number, here I think pstart
> is pointing to some logical block location..
>
> > struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);
> >
> > /* do normalize only data requests, metadata requests
> > @@ -3029,7 +3030,7 @@ static void ext4_mb_normalize_request(st
> >
> > /* first, try to predict filesize */
> > /* XXX: should this table be tunable? */
> > - start = 0;
> > + pstart = 0;
> > if (size <= 16 * 1024) {
> > size = 16 * 1024;
> > } else if (size <= 32 * 1024) {
> > @@ -3045,25 +3046,25 @@ static void ext4_mb_normalize_request(st
> > } else if (size <= 1024 * 1024) {
> > size = 1024 * 1024;
> > } else if (NRL_CHECK_SIZE(size, 4 * 1024 * 1024, max, bsbits)) {
> > - start = ac->ac_o_ex.fe_logical << bsbits;
> > - start = (start / (1024 * 1024)) * (1024 * 1024);
> > + pstart = ac->ac_o_ex.fe_logical << bsbits;
> > + pstart = (pstart / (1024 * 1024)) * (1024 * 1024);
>
> How about using shift...
>
> - start = ac->ac_o_ex.fe_logical << bsbits;
> - start = (start / (1024 * 1024)) * (1024 * 1024);
> + start = (ac->ac_o_ex.fe_logical >> (20-bsbits)) << 20;
>
> That would be more efficient and should fix the overflow issue
>
> > size = 1024 * 1024;
> > } else if (NRL_CHECK_SIZE(size, 8 * 1024 * 1024, max, bsbits)) {
> > - start = ac->ac_o_ex.fe_logical << bsbits;
> > - start = (start / (4 * (1024 * 1024))) * 4 * (1024 * 1024);
> > + pstart = ac->ac_o_ex.fe_logical << bsbits;
> > + pstart = (pstart / (4 * (1024 * 1024))) * 4 * (1024 * 1024);
>
> + start = (ac->ac_o_ex.fe_logical >> (22-bsbits)) << 22;
>
> > size = 4 * 1024 * 1024;
> > } else if(NRL_CHECK_SIZE(ac->ac_o_ex.fe_len,(8<<20)>>bsbits,max,bsbits)){
> > - start = ac->ac_o_ex.fe_logical;
> > - start = start << bsbits;
> > - start = (start / (8 * (1024 * 1024))) * 8 * (1024 * 1024);
> > + pstart = ac->ac_o_ex.fe_logical;
> > + pstart = pstart << bsbits;
> > + pstart = (pstart / (8 * (1024 * 1024))) * 8 * (1024 * 1024);
>
> + start = (ac->ac_o_ex.fe_logical >> (23-bsbits)) << 23;
>
> > size = 8 * 1024 * 1024;
> > } else {
> > - start = ac->ac_o_ex.fe_logical;
> > - start = start << bsbits;
> > + pstart = ac->ac_o_ex.fe_logical;
> > + pstart = pstart << bsbits;
> > size = ac->ac_o_ex.fe_len << bsbits;
What about this ? I guess we will overflow
start = start << bsbits;
I guess start should be of type loff_t. Patch below
-aneesh
ext4: Fix overflow in ext4_mb_normalize_request
From: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
kernel BUG at fs/ext4/mballoc.c:3148!
The BUG_ON is:
BUG_ON(size <= 0 || size >= EXT4_BLOCKS_PER_GROUP(ac->ac_sb));
where the value of "size" is 4293920768.
This is due to the overflow of the variable "start" in the
ext4_mb_normalize_request() function.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
---
fs/ext4/mballoc.c | 21 ++++++++-------------
1 files changed, 8 insertions(+), 13 deletions(-)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index d8cd81e..d8a2db8 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2998,7 +2998,7 @@ static void ext4_mb_normalize_request(struct ext4_allocation_context *ac,
int bsbits, max;
ext4_lblk_t end;
struct list_head *cur;
- loff_t size, orig_size;
+ loff_t size, orig_size, start_off;
ext4_lblk_t start, orig_start;
struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);
@@ -3039,7 +3039,7 @@ static void ext4_mb_normalize_request(struct ext4_allocation_context *ac,
/* first, try to predict filesize */
/* XXX: should this table be tunable? */
- start = 0;
+ start_off = 0;
if (size <= 16 * 1024) {
size = 16 * 1024;
} else if (size <= 32 * 1024) {
@@ -3055,26 +3055,21 @@ static void ext4_mb_normalize_request(struct ext4_allocation_context *ac,
} else if (size <= 1024 * 1024) {
size = 1024 * 1024;
} else if (NRL_CHECK_SIZE(size, 4 * 1024 * 1024, max, bsbits)) {
- start = ac->ac_o_ex.fe_logical << bsbits;
- start = (start / (1024 * 1024)) * (1024 * 1024);
+ start_off = (ac->ac_o_ex.fe_logical >> (20 - bsbits)) << 20;
size = 1024 * 1024;
} else if (NRL_CHECK_SIZE(size, 8 * 1024 * 1024, max, bsbits)) {
- start = ac->ac_o_ex.fe_logical << bsbits;
- start = (start / (4 * (1024 * 1024))) * 4 * (1024 * 1024);
+ start_off = (ac->ac_o_ex.fe_logical >> (22 - bsbits)) << 22;
size = 4 * 1024 * 1024;
} else if (NRL_CHECK_SIZE(ac->ac_o_ex.fe_len,
(8<<20)>>bsbits, max, bsbits)) {
- start = ac->ac_o_ex.fe_logical;
- start = start << bsbits;
- start = (start / (8 * (1024 * 1024))) * 8 * (1024 * 1024);
+ start_off = (ac->ac_o_ex.fe_logical >> (23 - bsbits)) << 23;
size = 8 * 1024 * 1024;
} else {
- start = ac->ac_o_ex.fe_logical;
- start = start << bsbits;
- size = ac->ac_o_ex.fe_len << bsbits;
+ start_off = ac->ac_o_ex.fe_logical << bsbits;
+ size = ac->ac_o_ex.fe_len << bsbits;
}
orig_size = size = size >> bsbits;
- orig_start = start = start >> bsbits;
+ orig_start = start = start_off >> bsbits;
/* don't cover already allocated blocks in selected range */
if (ar->pleft && start <= ar->lleft) {
-
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