[PATCH] cifs: dir: fix memory leak in cifs_mknod

[PATCH] cifs: dir: fix memory leak in cifs_mknod

[Gustavo A. R. Silva]

Free allocated memory for full_path and xid before return.

Addresses-Coverity-ID: 1468029 ("Resource leak")
Fixes: 49162bfde140 ("cifs: do not allow creating sockets except with
SMB1 posix exensions")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 fs/cifs/dir.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index f0a759d..71e32d9 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -684,8 +684,11 @@ int cifs_mknod(struct inode *inode, struct dentry *direntry, umode_t mode,
 		goto mknod_out;
 	}
 
-	if (!S_ISCHR(mode) && !S_ISBLK(mode))
+	if (!S_ISCHR(mode) && !S_ISBLK(mode)) {
+		kfree(full_path);
+		free_xid(xid);
 		return -EPERM;
+	}
 
 	if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_UNX_EMUL))
 		goto mknod_out;
-- 
2.7.4

Re: [PATCH] cifs: dir: fix memory leak in cifs_mknod

[Steve French]

[-- Attachment #1: Type: text/plain, Size: 1638 bytes --]

I noticed a similar problem with the tcon link leak on that (which
Colin and Gustavo pointed out - thank you!) but also in another return
statement, so updated the original patch of Ronnie's merging the fixes

https://git.samba.org/sfrench/cifs-2.6.git/?p=sfrench/cifs-2.6.git;a=commit;h=167bc5de08dc97695f9d5c7069c3e69f409ff80b


Let me know if you see any problems with it.

On Fri, Apr 20, 2018 at 8:19 AM, Gustavo A. R. Silva
<gustavo@embeddedor.com> wrote:
> Free allocated memory for full_path and xid before return.
>
> Addresses-Coverity-ID: 1468029 ("Resource leak")
> Fixes: 49162bfde140 ("cifs: do not allow creating sockets except with
> SMB1 posix exensions")
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>  fs/cifs/dir.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
> index f0a759d..71e32d9 100644
> --- a/fs/cifs/dir.c
> +++ b/fs/cifs/dir.c
> @@ -684,8 +684,11 @@ int cifs_mknod(struct inode *inode, struct dentry *direntry, umode_t mode,
>                 goto mknod_out;
>         }
>
> -       if (!S_ISCHR(mode) && !S_ISBLK(mode))
> +       if (!S_ISCHR(mode) && !S_ISBLK(mode)) {
> +               kfree(full_path);
> +               free_xid(xid);
>                 return -EPERM;
> +       }
>
>         if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_UNX_EMUL))
>                 goto mknod_out;
> --
> 2.7.4
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-cifs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html



-- 
Thanks,

Steve

[-- Attachment #2: 0001-cifs-do-not-allow-creating-sockets-except-with-SMB1-.patch --]
[-- Type: text/x-patch, Size: 2395 bytes --]

From 167bc5de08dc97695f9d5c7069c3e69f409ff80b Mon Sep 17 00:00:00 2001
From: Steve French <smfrench@gmail.com>
Date: Fri, 20 Apr 2018 12:19:07 -0500
Subject: [PATCH 1/2] cifs: do not allow creating sockets except with SMB1
 posix exensions

RHBZ: 1453123

Since at least the 3.10 kernel and likely a lot earlier we have
not been able to create unix domain sockets in a cifs share
when mounted using the SFU mount option (except when mounted
with the cifs unix extensions to Samba e.g.)
Trying to create a socket, for example using the af_unix command from
xfstests will cause :
BUG: unable to handle kernel NULL pointer dereference at 00000000
00000040

Since no one uses or depends on being able to create unix domains sockets
on a cifs share the easiest fix to stop this vulnerability is to simply
not allow creation of any other special files than char or block devices
when sfu is used.

Added update to Ronnie's patch to handle a tcon link leak, and
to address a buf leak noticed by Gustavo and Colin.

CC: Gustavo A. R. Silva <gustavo@embeddedor.com>
CC:  Colin Ian King <colin.king@canonical.com>
Reported-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
Cc: stable@vger.kernel.org
---
 fs/cifs/dir.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index 81ba6e0d88d8..925844343038 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -684,6 +684,9 @@ int cifs_mknod(struct inode *inode, struct dentry *direntry, umode_t mode,
 		goto mknod_out;
 	}
 
+	if (!S_ISCHR(mode) && !S_ISBLK(mode))
+		goto mknod_out;
+
 	if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_UNX_EMUL))
 		goto mknod_out;
 
@@ -692,10 +695,8 @@ int cifs_mknod(struct inode *inode, struct dentry *direntry, umode_t mode,
 
 	buf = kmalloc(sizeof(FILE_ALL_INFO), GFP_KERNEL);
 	if (buf == NULL) {
-		kfree(full_path);
 		rc = -ENOMEM;
-		free_xid(xid);
-		return rc;
+		goto mknod_out;
 	}
 
 	if (backup_cred(cifs_sb))
@@ -742,7 +743,7 @@ int cifs_mknod(struct inode *inode, struct dentry *direntry, umode_t mode,
 		pdev->minor = cpu_to_le64(MINOR(device_number));
 		rc = tcon->ses->server->ops->sync_write(xid, &fid, &io_parms,
 							&bytes_written, iov, 1);
-	} /* else if (S_ISFIFO) */
+	}
 	tcon->ses->server->ops->close(xid, tcon, &fid);
 	d_drop(direntry);
 
-- 
2.14.1

Re: [PATCH] cifs: dir: fix memory leak in cifs_mknod

[Gustavo A. R. Silva]

Hi Steve,

On 04/20/2018 12:37 PM, Steve French wrote:
> I noticed a similar problem with the tcon link leak on that (which
> Colin and Gustavo pointed out - thank you!) but also in another return
> statement, so updated the original patch of Ronnie's merging the fixes
> 
> https://git.samba.org/sfrench/cifs-2.6.git/?p=sfrench/cifs-2.6.git;a=commit;h=167bc5de08dc97695f9d5c7069c3e69f409ff80b
> 
> 
> Let me know if you see any problems with it.
> 

Looks correct to me.

Thanks
--
Gustavo

> On Fri, Apr 20, 2018 at 8:19 AM, Gustavo A. R. Silva
> <gustavo@embeddedor.com> wrote:
>> Free allocated memory for full_path and xid before return.
>>
>> Addresses-Coverity-ID: 1468029 ("Resource leak")
>> Fixes: 49162bfde140 ("cifs: do not allow creating sockets except with
>> SMB1 posix exensions")
>> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
>> ---
>>   fs/cifs/dir.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
>> index f0a759d..71e32d9 100644
>> --- a/fs/cifs/dir.c
>> +++ b/fs/cifs/dir.c
>> @@ -684,8 +684,11 @@ int cifs_mknod(struct inode *inode, struct dentry *direntry, umode_t mode,
>>                  goto mknod_out;
>>          }
>>
>> -       if (!S_ISCHR(mode) && !S_ISBLK(mode))
>> +       if (!S_ISCHR(mode) && !S_ISBLK(mode)) {
>> +               kfree(full_path);
>> +               free_xid(xid);
>>                  return -EPERM;
>> +       }
>>
>>          if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_UNX_EMUL))
>>                  goto mknod_out;
>> --
>> 2.7.4
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-cifs" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> 
> 

Re: [PATCH] cifs: dir: fix memory leak in cifs_mknod

[Pavel Shilovsky]

2018-04-20 10:37 GMT-07:00 Steve French <smfrench@gmail.com>:
> I noticed a similar problem with the tcon link leak on that (which
> Colin and Gustavo pointed out - thank you!) but also in another return
> statement, so updated the original patch of Ronnie's merging the fixes
>
> https://git.samba.org/sfrench/cifs-2.6.git/?p=sfrench/cifs-2.6.git;a=commit;h=167bc5de08dc97695f9d5c7069c3e69f409ff80b
>
>
> Let me know if you see any problems with it.
>

Looks good.

Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>

--
Best regards,
Pavel Shilovsky