* [BUG]Missing i_sb NULL pointer check in destroy_inode()
[not found] ` <20031109152936.3a9ffb69.akpm@osdl.org>
@ 2003-11-24 19:00 ` Mingming Cao
2003-11-24 19:27 ` Andrew Morton
2003-11-25 8:36 ` Christoph Hellwig
0 siblings, 2 replies; 6+ messages in thread
From: Mingming Cao @ 2003-11-24 19:00 UTC (permalink / raw)
To: Andrew Morton, linux-kernel, marcelo.tosatti; +Cc: Paul.McKenney
Hello, Andrew, Marcelo,
destroy_inode() dereferences inode->i_sb without checking if it is NULL.
This is inconsistent with its caller: iput() and clear_inode(), both of
which check inode->i_sb before dereferencing it. Since iput() calls
destroy_inode() after calling file system's .clear_inode method(via
clear_inode()), some file systems might choose to clear the i_sb in the
.clear_inode super block operation. This results in a crash in
destroy_inode().
This issue exists in both 2.6, 2.4 and 2.4 kernel. A simple fix against
2.6.0-test9 is included below. 2.4 based fix should be very similar to
this one. Please take a look and consider include it.
Many thanks!!
--Mingming
----------------------------------------------------------
diff -urNp linux-2.6.0-test9/fs/inode.c a/fs/inode.c
--- linux-2.6.0-test9/fs/inode.c 2003-10-25 11:44:53.000000000 -0700
+++ a/fs/inode.c 2003-11-20 17:28:04.000000000 -0800
@@ -160,7 +160,7 @@ void destroy_inode(struct inode *inode)
if (inode_has_buffers(inode))
BUG();
security_inode_free(inode);
- if (inode->i_sb->s_op->destroy_inode)
+ if (inode->i_sb && inode->i_sb->s_op->destroy_inode)
inode->i_sb->s_op->destroy_inode(inode);
else
kmem_cache_free(inode_cachep, (inode));
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [BUG]Missing i_sb NULL pointer check in destroy_inode()
2003-11-24 19:00 ` [BUG]Missing i_sb NULL pointer check in destroy_inode() Mingming Cao
@ 2003-11-24 19:27 ` Andrew Morton
2003-11-24 20:10 ` Mingming Cao
2003-11-25 8:36 ` Christoph Hellwig
1 sibling, 1 reply; 6+ messages in thread
From: Andrew Morton @ 2003-11-24 19:27 UTC (permalink / raw)
To: Mingming Cao; +Cc: linux-kernel, marcelo.tosatti, Paul.McKenney
Mingming Cao <cmm@us.ibm.com> wrote:
>
> destroy_inode() dereferences inode->i_sb without checking if it is NULL.
> This is inconsistent with its caller: iput() and clear_inode(), both of
> which check inode->i_sb before dereferencing it.
I assume this has only been observed with an out-of-tree filesystem, but
yes, the consistency is good.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [BUG]Missing i_sb NULL pointer check in destroy_inode()
2003-11-24 19:27 ` Andrew Morton
@ 2003-11-24 20:10 ` Mingming Cao
0 siblings, 0 replies; 6+ messages in thread
From: Mingming Cao @ 2003-11-24 20:10 UTC (permalink / raw)
To: Andrew Morton; +Cc: linux-kernel, marcelo.tosatti, Paul.McKenney
On Mon, 2003-11-24 at 11:27, Andrew Morton wrote:
> Mingming Cao <cmm@us.ibm.com> wrote:
> >
> > destroy_inode() dereferences inode->i_sb without checking if it is NULL.
> > This is inconsistent with its caller: iput() and clear_inode(), both of
> > which check inode->i_sb before dereferencing it.
>
> I assume this has only been observed with an out-of-tree filesystem, but
> yes, the consistency is good.
>
Yes, the crash happened with an out-of-tree filesystem. Thanks.
-Mingming
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [BUG]Missing i_sb NULL pointer check in destroy_inode()
2003-11-24 19:00 ` [BUG]Missing i_sb NULL pointer check in destroy_inode() Mingming Cao
2003-11-24 19:27 ` Andrew Morton
@ 2003-11-25 8:36 ` Christoph Hellwig
2003-11-26 22:09 ` Mingming Cao
1 sibling, 1 reply; 6+ messages in thread
From: Christoph Hellwig @ 2003-11-25 8:36 UTC (permalink / raw)
To: Mingming Cao; +Cc: Andrew Morton, linux-kernel, marcelo.tosatti, Paul.McKenney
On Mon, Nov 24, 2003 at 11:00:38AM -0800, Mingming Cao wrote:
> Hello, Andrew, Marcelo,
>
> destroy_inode() dereferences inode->i_sb without checking if it is NULL.
> This is inconsistent with its caller: iput() and clear_inode(), both of
> which check inode->i_sb before dereferencing it. Since iput() calls
> destroy_inode() after calling file system's .clear_inode method(via
> clear_inode()), some file systems might choose to clear the i_sb in the
> .clear_inode super block operation. This results in a crash in
> destroy_inode().
>
> This issue exists in both 2.6, 2.4 and 2.4 kernel. A simple fix against
> 2.6.0-test9 is included below. 2.4 based fix should be very similar to
> this one. Please take a look and consider include it.
inode->i_sb can't be NULL. We should remove all those checks.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [BUG]Missing i_sb NULL pointer check in destroy_inode()
2003-11-25 8:36 ` Christoph Hellwig
@ 2003-11-26 22:09 ` Mingming Cao
2003-11-27 1:10 ` Timo Kamph
0 siblings, 1 reply; 6+ messages in thread
From: Mingming Cao @ 2003-11-26 22:09 UTC (permalink / raw)
To: Christoph Hellwig
Cc: Andrew Morton, linux-kernel, marcelo.tosatti, Paul.McKenney
On Tue, 2003-11-25 at 00:36, Christoph Hellwig wrote:
> On Mon, Nov 24, 2003 at 11:00:38AM -0800, Mingming Cao wrote:
> > Hello, Andrew, Marcelo,
> >
> > destroy_inode() dereferences inode->i_sb without checking if it is NULL.
> > This is inconsistent with its caller: iput() and clear_inode(), both of
> > which check inode->i_sb before dereferencing it. Since iput() calls
> > destroy_inode() after calling file system's .clear_inode method(via
> > clear_inode()), some file systems might choose to clear the i_sb in the
> > .clear_inode super block operation. This results in a crash in
> > destroy_inode().
> >
> > This issue exists in both 2.6, 2.4 and 2.4 kernel. A simple fix against
> > 2.6.0-test9 is included below. 2.4 based fix should be very similar to
> > this one. Please take a look and consider include it.
>
> inode->i_sb can't be NULL. We should remove all those checks.
>
Sorry I can not agree with this. Maybe the inode->i_sb should not be
NULL, but the kernel still allows the file system to do so. In fact
JFS's diReadSpecial() function clears the inode->i_sb to NULL before
calling iput().
Acutally iput() in 2.6 is missing the check too.(in 2.4 the check is
there). Here is the the incremental fix for 2.6 only:
diff -urNp linux-2.6.0-test10/fs/inode.c a/fs/inode.c
--- linux-2.6.0-test10/fs/inode.c 2003-11-23 17:33:24.000000000 -0800
+++ a/fs/inode.c 2003-11-26 13:59:34.000000000 -0800
@@ -1084,13 +1084,13 @@ static inline void iput_final(struct ino
void iput(struct inode *inode)
{
if (inode) {
- struct super_operations *op = inode->i_sb->s_op;
-
+ struct super_block *sb = inode->i_sb;
+
if (inode->i_state == I_CLEAR)
BUG();
- if (op && op->put_inode)
- op->put_inode(inode);
+ if (sb && sb->op && sb->op->put_inode)
+ sb->op->put_inode(inode);
if (atomic_dec_and_lock(&inode->i_count, &inode_lock))
iput_final(inode);
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [BUG]Missing i_sb NULL pointer check in destroy_inode()
2003-11-26 22:09 ` Mingming Cao
@ 2003-11-27 1:10 ` Timo Kamph
0 siblings, 0 replies; 6+ messages in thread
From: Timo Kamph @ 2003-11-27 1:10 UTC (permalink / raw)
To: Mingming Cao; +Cc: linux-kernel
On 26 Nov 2003 at 14:09, Mingming Cao wrote:
> On Tue, 2003-11-25 at 00:36, Christoph Hellwig wrote:
> > On Mon, Nov 24, 2003 at 11:00:38AM -0800, Mingming Cao wrote:
> > > Hello, Andrew, Marcelo,
> > >
> > > destroy_inode() dereferences inode->i_sb without checking if it is NULL.
> > > This is inconsistent with its caller: iput() and clear_inode(), both of
> > > which check inode->i_sb before dereferencing it. Since iput() calls
> > > destroy_inode() after calling file system's .clear_inode method(via
> > > clear_inode()), some file systems might choose to clear the i_sb in the
> > > .clear_inode super block operation. This results in a crash in
> > > destroy_inode().
> > >
> > > This issue exists in both 2.6, 2.4 and 2.4 kernel. A simple fix against
> > > 2.6.0-test9 is included below. 2.4 based fix should be very similar to
> > > this one. Please take a look and consider include it.
> >
> > inode->i_sb can't be NULL. We should remove all those checks.
> >
> Sorry I can not agree with this. Maybe the inode->i_sb should not be
> NULL, but the kernel still allows the file system to do so. In fact
> JFS's diReadSpecial() function clears the inode->i_sb to NULL before
> calling iput().
>
> Acutally iput() in 2.6 is missing the check too.(in 2.4 the check is
> there). Here is the the incremental fix for 2.6 only:
There is a little typo in your patch. The struct member is s_op and not op.
The following patch should be right.
Timo
diff -urNp linux-2.6.0-test10/fs/inode.c a/fs/inode.c
--- linux-2.6.0-test10/fs/inode.c 2003-11-23 17:33:24.000000000 -0800
+++ a/fs/inode.c 2003-11-26 13:59:34.000000000 -0800
@@ -1084,13 +1084,13 @@ static inline void iput_final(struct ino
void iput(struct inode *inode)
{
if (inode) {
- struct super_operations *op = inode->i_sb->s_op;
-
+ struct super_block *sb = inode->i_sb;
+
if (inode->i_state == I_CLEAR)
BUG();
- if (op && op->put_inode)
- op->put_inode(inode);
+ if (sb && sb->s_op && sb->s_op->put_inode)
+ sb->s_op->put_inode(inode);
if (atomic_dec_and_lock(&inode->i_count, &inode_lock))
iput_final(inode);
^ permalink raw reply [flat|nested] 6+ messages in thread
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2003-11-24 19:00 ` [BUG]Missing i_sb NULL pointer check in destroy_inode() Mingming Cao
2003-11-24 19:27 ` Andrew Morton
2003-11-24 20:10 ` Mingming Cao
2003-11-25 8:36 ` Christoph Hellwig
2003-11-26 22:09 ` Mingming Cao
2003-11-27 1:10 ` Timo Kamph
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