Re: [PATCH] btrfs: fix dereference on inode->i_sb before inode null check
On 12/16/16 7:20 AM, Colin King wrote:
> From: Colin Ian King
>
> inode is being deferenced and then inode is checked to see if it
> is null, implying we potentially could have a null pointer deference
> on inode.
>
> Found with static analysis by CoverityScan, CID 1389472
>
> Fix this by dereferencing inode only after the inode null check.
>
> Fixes: 0b246afa62b0cf5 ("btrfs: root->fs_info cleanup, add fs_info
> convenience variables")
Hi Colin -
Thanks for the review. The right fix here is to eliminate the tests for
inode == NULL entirely. This is a callback for exportfs, which will
itself crash if dentry->d_inode or parent->d_inode is NULL. Removing
the tests would be consistent with other file systems.
-Jeff
> Signed-off-by: Colin Ian King
> ---
> fs/btrfs/export.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/export.c b/fs/btrfs/export.c
> index 340d907..b746d2b 100644
> --- a/fs/btrfs/export.c
> +++ b/fs/btrfs/export.c
> @@ -223,7 +223,7 @@ static int btrfs_get_name(struct dentry *parent, char
> *name,
> {
> struct inode *inode = d_inode(child);
> struct inode *dir = d_inode(parent);
> - struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
> + struct btrfs_fs_info *fs_info;
> struct btrfs_path *path;
> struct btrfs_root *root = BTRFS_I(dir)->root;
> struct btrfs_inode_ref *iref;
> @@ -241,6 +241,7 @@ static int btrfs_get_name(struct dentry *parent, char
> *name,
> if (!S_ISDIR(dir->i_mode))
> return -EINVAL;
>
> + fs_info = btrfs_sb(inode->i_sb);
> ino = btrfs_ino(inode);
>
> path = btrfs_alloc_path();
>
--
Jeff Mahoney
SUSE Labs
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Re: [PATCH] btrfs: fix dereference on inode->i_sb before inode null check
On 16/12/16 15:03, Jeff Mahoney wrote:
> On 12/16/16 7:20 AM, Colin King wrote:
>> From: Colin Ian King
>>
>> inode is being deferenced and then inode is checked to see if it
>> is null, implying we potentially could have a null pointer deference
>> on inode.
>>
>> Found with static analysis by CoverityScan, CID 1389472
>>
>> Fix this by dereferencing inode only after the inode null check.
>>
>> Fixes: 0b246afa62b0cf5 ("btrfs: root->fs_info cleanup, add fs_info
>> convenience variables")
>
> Hi Colin -
>
> Thanks for the review. The right fix here is to eliminate the tests for
> inode == NULL entirely. This is a callback for exportfs, which will
> itself crash if dentry->d_inode or parent->d_inode is NULL. Removing
> the tests would be consistent with other file systems.
Ah, thanks for pointing that out. New patch on it's way soon.
Colin
>
> -Jeff
>
>> Signed-off-by: Colin Ian King
>> ---
>> fs/btrfs/export.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/btrfs/export.c b/fs/btrfs/export.c
>> index 340d907..b746d2b 100644
>> --- a/fs/btrfs/export.c
>> +++ b/fs/btrfs/export.c
>> @@ -223,7 +223,7 @@ static int btrfs_get_name(struct dentry *parent, char
>> *name,
>> {
>> struct inode *inode = d_inode(child);
>> struct inode *dir = d_inode(parent);
>> -struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
>> +struct btrfs_fs_info *fs_info;
>> struct btrfs_path *path;
>> struct btrfs_root *root = BTRFS_I(dir)->root;
>> struct btrfs_inode_ref *iref;
>> @@ -241,6 +241,7 @@ static int btrfs_get_name(struct dentry *parent, char
>> *name,
>> if (!S_ISDIR(dir->i_mode))
>> return -EINVAL;
>>
>> +fs_info = btrfs_sb(inode->i_sb);
>> ino = btrfs_ino(inode);
>>
>> path = btrfs_alloc_path();
>>
>
>
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Description: OpenPGP digital signature
[PATCH] btrfs: fix dereference on inode->i_sb before inode null check
From: Colin Ian King
inode is being deferenced and then inode is checked to see if it
is null, implying we potentially could have a null pointer deference
on inode.
Found with static analysis by CoverityScan, CID 1389472
Fix this by dereferencing inode only after the inode null check.
Fixes: 0b246afa62b0cf5 ("btrfs: root->fs_info cleanup, add fs_info convenience
variables")
Signed-off-by: Colin Ian King
---
fs/btrfs/export.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/export.c b/fs/btrfs/export.c
index 340d907..b746d2b 100644
--- a/fs/btrfs/export.c
+++ b/fs/btrfs/export.c
@@ -223,7 +223,7 @@ static int btrfs_get_name(struct dentry *parent, char *name,
{
struct inode *inode = d_inode(child);
struct inode *dir = d_inode(parent);
- struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
+ struct btrfs_fs_info *fs_info;
struct btrfs_path *path;
struct btrfs_root *root = BTRFS_I(dir)->root;
struct btrfs_inode_ref *iref;
@@ -241,6 +241,7 @@ static int btrfs_get_name(struct dentry *parent, char *name,
if (!S_ISDIR(dir->i_mode))
return -EINVAL;
+ fs_info = btrfs_sb(inode->i_sb);
ino = btrfs_ino(inode);
path = btrfs_alloc_path();
--
2.10.2
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