smackfs: restrict bytes count in smackfs write functions
diff mbox series

Message ID 20210124143627.582115-1-snovitoll@gmail.com
State New, archived
Headers show
Series
  • smackfs: restrict bytes count in smackfs write functions
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Commit Message

Sabyrzhan Tasbolatov Jan. 24, 2021, 2:36 p.m. UTC
syzbot found WARNINGs in several smackfs write operations where
bytes count is passed to memdup_user_nul which exceeds
GFP MAX_ORDER. Check count size if bigger SMK_LONGLABEL,
for smk_write_syslog if bigger than PAGE_SIZE - 1.

Reported-by: syzbot+a71a442385a0b2815497@syzkaller.appspotmail.com
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
---
 security/smack/smackfs.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Comments

Casey Schaufler Jan. 25, 2021, 6:08 p.m. UTC | #1
On 1/24/2021 6:36 AM, Sabyrzhan Tasbolatov wrote:
> syzbot found WARNINGs in several smackfs write operations where
> bytes count is passed to memdup_user_nul which exceeds
> GFP MAX_ORDER. Check count size if bigger SMK_LONGLABEL,
> for smk_write_syslog if bigger than PAGE_SIZE - 1.
>
> Reported-by: syzbot+a71a442385a0b2815497@syzkaller.appspotmail.com
> Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>

Thank you for the patch. Unfortunately, SMK_LONGLABEL isn't
the right value in some of these cases. 

> ---
>  security/smack/smackfs.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
> index 5d44b7d258ef..88678c6f1b8c 100644
> --- a/security/smack/smackfs.c
> +++ b/security/smack/smackfs.c
> @@ -1167,7 +1167,7 @@ static ssize_t smk_write_net4addr(struct file *file, const char __user *buf,
>  		return -EPERM;
>  	if (*ppos != 0)
>  		return -EINVAL;
> -	if (count < SMK_NETLBLADDRMIN)
> +	if (count < SMK_NETLBLADDRMIN || count > SMK_LONGLABEL)
>  		return -EINVAL;
>  
>  	data = memdup_user_nul(buf, count);
> @@ -1427,7 +1427,7 @@ static ssize_t smk_write_net6addr(struct file *file, const char __user *buf,
>  		return -EPERM;
>  	if (*ppos != 0)
>  		return -EINVAL;
> -	if (count < SMK_NETLBLADDRMIN)
> +	if (count < SMK_NETLBLADDRMIN || count > SMK_LONGLABEL)
>  		return -EINVAL;
>  
>  	data = memdup_user_nul(buf, count);
> @@ -2647,6 +2647,8 @@ static ssize_t smk_write_syslog(struct file *file, const char __user *buf,
>  
>  	if (!smack_privileged(CAP_MAC_ADMIN))
>  		return -EPERM;
> +	if (count > PAGE_SIZE - 1)
> +		return -EINVAL;
>  
>  	data = memdup_user_nul(buf, count);
>  	if (IS_ERR(data))
> @@ -2744,6 +2746,8 @@ static ssize_t smk_write_relabel_self(struct file *file, const char __user *buf,
>  	 */
>  	if (*ppos != 0)
>  		return -EINVAL;
> +	if (count > SMK_LONGLABEL)
> +		return -EINVAL;
>  
>  	data = memdup_user_nul(buf, count);
>  	if (IS_ERR(data))
Tetsuo Handa Jan. 25, 2021, 10:42 p.m. UTC | #2
On 2021/01/26 3:08, Casey Schaufler wrote:
> On 1/24/2021 6:36 AM, Sabyrzhan Tasbolatov wrote:
>> syzbot found WARNINGs in several smackfs write operations where
>> bytes count is passed to memdup_user_nul which exceeds
>> GFP MAX_ORDER. Check count size if bigger SMK_LONGLABEL,
>> for smk_write_syslog if bigger than PAGE_SIZE - 1.
>>
>> Reported-by: syzbot+a71a442385a0b2815497@syzkaller.appspotmail.com
>> Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
> 
> Thank you for the patch. Unfortunately, SMK_LONGLABEL isn't
> the right value in some of these cases. 
> 

Since it uses sscanf(), I think that whitespaces must be excluded from upper limit
check. I'm proposing adding __GFP_NOWARM on the memdup_user_nul() side at
https://lkml.kernel.org/r/20210120103436.11830-1-penguin-kernel@I-love.SAKURA.ne.jp .

Patch
diff mbox series

diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index 5d44b7d258ef..88678c6f1b8c 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -1167,7 +1167,7 @@  static ssize_t smk_write_net4addr(struct file *file, const char __user *buf,
 		return -EPERM;
 	if (*ppos != 0)
 		return -EINVAL;
-	if (count < SMK_NETLBLADDRMIN)
+	if (count < SMK_NETLBLADDRMIN || count > SMK_LONGLABEL)
 		return -EINVAL;
 
 	data = memdup_user_nul(buf, count);
@@ -1427,7 +1427,7 @@  static ssize_t smk_write_net6addr(struct file *file, const char __user *buf,
 		return -EPERM;
 	if (*ppos != 0)
 		return -EINVAL;
-	if (count < SMK_NETLBLADDRMIN)
+	if (count < SMK_NETLBLADDRMIN || count > SMK_LONGLABEL)
 		return -EINVAL;
 
 	data = memdup_user_nul(buf, count);
@@ -2647,6 +2647,8 @@  static ssize_t smk_write_syslog(struct file *file, const char __user *buf,
 
 	if (!smack_privileged(CAP_MAC_ADMIN))
 		return -EPERM;
+	if (count > PAGE_SIZE - 1)
+		return -EINVAL;
 
 	data = memdup_user_nul(buf, count);
 	if (IS_ERR(data))
@@ -2744,6 +2746,8 @@  static ssize_t smk_write_relabel_self(struct file *file, const char __user *buf,
 	 */
 	if (*ppos != 0)
 		return -EINVAL;
+	if (count > SMK_LONGLABEL)
+		return -EINVAL;
 
 	data = memdup_user_nul(buf, count);
 	if (IS_ERR(data))