[PATCH 0/1] nilfs2: fix potential memory overrun on inode

[PATCH 0/1] nilfs2: fix potential memory overrun on inode

[Ryusuke Konishi]

Hi Andrew,

please queue the following patch as a bug fix.  It fixes a memory
overrun issue recently I found in the b-tree implementation of nilfs2.

Thanks,
Ryusuke Konishi
--
Ryusuke Konishi (1):
      nilfs2: fix potential memory overrun on inode

 fs/nilfs2/btree.c | 47 ++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 44 insertions(+), 3 deletions(-)

[PATCH 1/1] nilfs2: fix potential memory overrun on inode

[Ryusuke Konishi]

Each inode of nilfs2 stores a root node of a b-tree, and it turned out
to have a memory overrun issue:

Each b-tree node of nilfs2 stores a set of key-value pairs and the
number of them (in "bn_nchildren" member of nilfs_btree_node struct),
as well as a few other "bn_*" members.

Since the value of "bn_nchildren" is used for operations on the
key-values within the b-tree node, it can cause memory access overrun
if a large number is incorrectly set to "bn_nchildren".

For instance, nilfs_btree_node_lookup() function determines the range
of binary search with it, and too large "bn_nchildren" leads
nilfs_btree_node_get_key() in that function to overrun.

As for intermediate b-tree nodes, this is prevented by a sanity check
performed when each node is read from a drive, however, no sanity
check has been done for root nodes stored in inodes.

This patch fixes the issue by adding missing sanity check against
b-tree root nodes so that it's called when on-memory inodes are read
from ifile, inode metadata file.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
---
 fs/nilfs2/btree.c | 47 ++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 44 insertions(+), 3 deletions(-)

diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
index b2e3ff3..c645d7c 100644
--- a/fs/nilfs2/btree.c
+++ b/fs/nilfs2/btree.c
@@ -31,6 +31,8 @@
 #include "alloc.h"
 #include "dat.h"
 
+static void __nilfs_btree_init(struct nilfs_bmap *bmap);
+
 static struct nilfs_btree_path *nilfs_btree_alloc_path(void)
 {
 	struct nilfs_btree_path *path;
@@ -368,6 +370,34 @@ static int nilfs_btree_node_broken(const struct nilfs_btree_node *node,
 	return ret;
 }
 
+/**
+ * nilfs_btree_root_broken - verify consistency of btree root node
+ * @node: btree root node to be examined
+ * @ino: inode number
+ *
+ * Return Value: If node is broken, 1 is returned. Otherwise, 0 is returned.
+ */
+static int nilfs_btree_root_broken(const struct nilfs_btree_node *node,
+				   ino_t ino)
+{
+	int level, flags, nchildren;
+	int ret = 0;
+
+	level = nilfs_btree_node_get_level(node);
+	flags = nilfs_btree_node_get_flags(node);
+	nchildren = nilfs_btree_node_get_nchildren(node);
+
+	if (unlikely(level < NILFS_BTREE_LEVEL_NODE_MIN ||
+		     level > NILFS_BTREE_LEVEL_MAX ||
+		     nchildren < 0 ||
+		     nchildren > NILFS_BTREE_ROOT_NCHILDREN_MAX)) {
+		pr_crit("NILFS: bad btree root (inode number=%lu): level = %d, flags = 0x%x, nchildren = %d\n",
+			ino, level, flags, nchildren);
+		ret = 1;
+	}
+	return ret;
+}
+
 int nilfs_btree_broken_node_block(struct buffer_head *bh)
 {
 	int ret;
@@ -1713,7 +1743,7 @@ nilfs_btree_commit_convert_and_insert(struct nilfs_bmap *btree,
 
 	/* convert and insert */
 	dat = NILFS_BMAP_USE_VBN(btree) ? nilfs_bmap_get_dat(btree) : NULL;
-	nilfs_btree_init(btree);
+	__nilfs_btree_init(btree);
 	if (nreq != NULL) {
 		nilfs_bmap_commit_alloc_ptr(btree, dreq, dat);
 		nilfs_bmap_commit_alloc_ptr(btree, nreq, dat);
@@ -2294,12 +2324,23 @@ static const struct nilfs_bmap_operations nilfs_btree_ops_gc = {
 	.bop_gather_data	=	NULL,
 };
 
-int nilfs_btree_init(struct nilfs_bmap *bmap)
+static void __nilfs_btree_init(struct nilfs_bmap *bmap)
 {
 	bmap->b_ops = &nilfs_btree_ops;
 	bmap->b_nchildren_per_block =
 		NILFS_BTREE_NODE_NCHILDREN_MAX(nilfs_btree_node_size(bmap));
-	return 0;
+}
+
+int nilfs_btree_init(struct nilfs_bmap *bmap)
+{
+	int ret = 0;
+
+	__nilfs_btree_init(bmap);
+
+	if (nilfs_btree_root_broken(nilfs_btree_get_root(bmap),
+				    bmap->b_inode->i_ino))
+		ret = -EIO;
+	return ret;
 }
 
 void nilfs_btree_init_gc(struct nilfs_bmap *bmap)
-- 
1.8.3.1

Re: [PATCH 1/1] nilfs2: fix potential memory overrun on inode

[Andrew Morton]

On Fri, 20 Feb 2015 22:46:35 +0900 Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> wrote:

> Each inode of nilfs2 stores a root node of a b-tree, and it turned out
> to have a memory overrun issue:
> 
> Each b-tree node of nilfs2 stores a set of key-value pairs and the
> number of them (in "bn_nchildren" member of nilfs_btree_node struct),
> as well as a few other "bn_*" members.
> 
> Since the value of "bn_nchildren" is used for operations on the
> key-values within the b-tree node, it can cause memory access overrun
> if a large number is incorrectly set to "bn_nchildren".
> 
> For instance, nilfs_btree_node_lookup() function determines the range
> of binary search with it, and too large "bn_nchildren" leads
> nilfs_btree_node_get_key() in that function to overrun.
> 
> As for intermediate b-tree nodes, this is prevented by a sanity check
> performed when each node is read from a drive, however, no sanity
> check has been done for root nodes stored in inodes.
> 
> This patch fixes the issue by adding missing sanity check against
> b-tree root nodes so that it's called when on-memory inodes are read
> from ifile, inode metadata file.

How would one trigger this overrun?  Mount an fs with a deliberately
corrupted/inconsistent fs image?

Memory overrun sounds nasty so I'm thinking we add cc:stable to this
one.  OK?

Re: [PATCH 1/1] nilfs2: fix potential memory overrun on inode

[Ryusuke Konishi]

On Fri, 20 Feb 2015 13:58:42 -0800, Andrew Morton wrote:
> On Fri, 20 Feb 2015 22:46:35 +0900 Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> wrote:
> 
>> Each inode of nilfs2 stores a root node of a b-tree, and it turned out
>> to have a memory overrun issue:
>> 
>> Each b-tree node of nilfs2 stores a set of key-value pairs and the
>> number of them (in "bn_nchildren" member of nilfs_btree_node struct),
>> as well as a few other "bn_*" members.
>> 
>> Since the value of "bn_nchildren" is used for operations on the
>> key-values within the b-tree node, it can cause memory access overrun
>> if a large number is incorrectly set to "bn_nchildren".
>> 
>> For instance, nilfs_btree_node_lookup() function determines the range
>> of binary search with it, and too large "bn_nchildren" leads
>> nilfs_btree_node_get_key() in that function to overrun.
>> 
>> As for intermediate b-tree nodes, this is prevented by a sanity check
>> performed when each node is read from a drive, however, no sanity
>> check has been done for root nodes stored in inodes.
>> 
>> This patch fixes the issue by adding missing sanity check against
>> b-tree root nodes so that it's called when on-memory inodes are read
>> from ifile, inode metadata file.
> 
> How would one trigger this overrun?  Mount an fs with a deliberately
> corrupted/inconsistent fs image?

Yes, this can be triggered by mounting an fs with a corrupted image
deliberately or by chance.

> Memory overrun sounds nasty so I'm thinking we add cc:stable to this
> one.  OK?

Agreed.

Ryusuke Konishi

Re: [PATCH 1/1] nilfs2: fix potential memory overrun on inode

[Ryusuke Konishi]

On Sat, 21 Feb 2015 09:22:08 +0900 (JST), Ryusuke Konishi wrote:
> On Fri, 20 Feb 2015 13:58:42 -0800, Andrew Morton wrote:
>> On Fri, 20 Feb 2015 22:46:35 +0900 Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> wrote:
>> 
>>> Each inode of nilfs2 stores a root node of a b-tree, and it turned out
>>> to have a memory overrun issue:
>>> 
>>> Each b-tree node of nilfs2 stores a set of key-value pairs and the
>>> number of them (in "bn_nchildren" member of nilfs_btree_node struct),
>>> as well as a few other "bn_*" members.
>>> 
>>> Since the value of "bn_nchildren" is used for operations on the
>>> key-values within the b-tree node, it can cause memory access overrun
>>> if a large number is incorrectly set to "bn_nchildren".
>>> 
>>> For instance, nilfs_btree_node_lookup() function determines the range
>>> of binary search with it, and too large "bn_nchildren" leads
>>> nilfs_btree_node_get_key() in that function to overrun.
>>> 
>>> As for intermediate b-tree nodes, this is prevented by a sanity check
>>> performed when each node is read from a drive, however, no sanity
>>> check has been done for root nodes stored in inodes.
>>> 
>>> This patch fixes the issue by adding missing sanity check against
>>> b-tree root nodes so that it's called when on-memory inodes are read
>>> from ifile, inode metadata file.
>> 
>> How would one trigger this overrun?  Mount an fs with a deliberately
>> corrupted/inconsistent fs image?
> 
> Yes, this can be triggered by mounting an fs with a corrupted image
> deliberately or by chance.
> 
>> Memory overrun sounds nasty so I'm thinking we add cc:stable to this
>> one.  OK?
> 
> Agreed.

Could you apply the following amendment ?

I've got a warning from 0day kernel testing backend:

    fs/nilfs2/btree.c: In function 'nilfs_btree_root_broken':
>> fs/nilfs2/btree.c:394:3: warning: format '%lu' expects argument of type 'long unsigned int', but argument 2 has type 'ino_t' [-Wformat=]
       pr_crit("NILFS: bad btree root (inode number=%lu): level = %d, 
flags = 0x%x, nchildren = %d\n",
       ^

This is output for s390 arch since ino_t doesn't mean "unsigned long"
in s390.

Thanks,
Ryusuke Konishi
--
diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
index c645d7c..ecdbae1 100644
--- a/fs/nilfs2/btree.c
+++ b/fs/nilfs2/btree.c
@@ -378,7 +378,7 @@ static int nilfs_btree_node_broken(const struct nilfs_btree_node *node,
  * Return Value: If node is broken, 1 is returned. Otherwise, 0 is returned.
  */
 static int nilfs_btree_root_broken(const struct nilfs_btree_node *node,
-				   ino_t ino)
+				   unsigned long ino)
 {
 	int level, flags, nchildren;
 	int ret = 0;
-- 
1.8.3.1

Re: [PATCH 1/1] nilfs2: fix potential memory overrun on inode

[Andrew Morton]

On Sat, 21 Feb 2015 10:13:28 +0900 (JST) Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> wrote:

> I've got a warning from 0day kernel testing backend:
> 
>     fs/nilfs2/btree.c: In function 'nilfs_btree_root_broken':
> >> fs/nilfs2/btree.c:394:3: warning: format '%lu' expects argument of type 'long unsigned int', but argument 2 has type 'ino_t' [-Wformat=]
>        pr_crit("NILFS: bad btree root (inode number=%lu): level = %d, 
> flags = 0x%x, nchildren = %d\n",
>        ^
> 
> This is output for s390 arch since ino_t doesn't mean "unsigned long"
> in s390.

alpha uses uint for ino_t as well.

It seems a bit pointless - neither arch uses ino_t in ./arch/ code.  I
suspect both could switch to ulong, which would make the world a
slightly better place.

Re: [PATCH 1/1] nilfs2: fix potential memory overrun on inode

[Ryusuke Konishi]

On Fri, 20 Feb 2015 18:00:55 -0800, Andrew Morton wrote:
> On Sat, 21 Feb 2015 10:13:28 +0900 (JST) Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> wrote:
> 
>> I've got a warning from 0day kernel testing backend:
>> 
>>     fs/nilfs2/btree.c: In function 'nilfs_btree_root_broken':
>> >> fs/nilfs2/btree.c:394:3: warning: format '%lu' expects argument of type 'long unsigned int', but argument 2 has type 'ino_t' [-Wformat=]
>>        pr_crit("NILFS: bad btree root (inode number=%lu): level = %d, 
>> flags = 0x%x, nchildren = %d\n",
>>        ^
>> 
>> This is output for s390 arch since ino_t doesn't mean "unsigned long"
>> in s390.
> 
> alpha uses uint for ino_t as well.
> 
> It seems a bit pointless - neither arch uses ino_t in ./arch/ code.  I
> suspect both could switch to ulong, which would make the world a
> slightly better place.

I entirely agree.

Regards,
Ryusuke Konishi