This is a note to let you know that I've just added the patch titled
smackfs: restrict bytes count in smackfs write functions
to the 5.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
smackfs-restrict-bytes-count-in-smackfs-write-functions.patch
and it can be found in the queue-5.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7ef4c19d245f3dc233fd4be5acea436edd1d83d8 Mon Sep 17 00:00:00 2001
From: Sabyrzhan Tasbolatov <snovitoll@xxxxxxxxx>
Date: Thu, 28 Jan 2021 17:58:01 +0600
Subject: smackfs: restrict bytes count in smackfs write functions
From: Sabyrzhan Tasbolatov <snovitoll@xxxxxxxxx>
commit 7ef4c19d245f3dc233fd4be5acea436edd1d83d8 upstream.
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 than PAGE_SIZE.
Per smackfs doc, smk_write_net4addr accepts any label or -CIPSO,
smk_write_net6addr accepts any label or -DELETE. I couldn't find
any general rule for other label lengths except SMK_LABELLEN,
SMK_LONGLABEL, SMK_CIPSOMAX which are documented.
Let's constrain, in general, smackfs label lengths for PAGE_SIZE.
Although fuzzer crashes write to smackfs/netlabel on 0x400000 length.
Here is a quick way to reproduce the WARNING:
python -c "print('A' * 0x400000)" > /sys/fs/smackfs/netlabel
Reported-by: syzbot+a71a442385a0b2815497@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@xxxxxxxxx>
Signed-off-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
security/smack/smackfs.c | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -1167,7 +1167,7 @@ static ssize_t smk_write_net4addr(struct
return -EPERM;
if (*ppos != 0)
return -EINVAL;
- if (count < SMK_NETLBLADDRMIN)
+ if (count < SMK_NETLBLADDRMIN || count > PAGE_SIZE - 1)
return -EINVAL;
data = memdup_user_nul(buf, count);
@@ -1427,7 +1427,7 @@ static ssize_t smk_write_net6addr(struct
return -EPERM;
if (*ppos != 0)
return -EINVAL;
- if (count < SMK_NETLBLADDRMIN)
+ if (count < SMK_NETLBLADDRMIN || count > PAGE_SIZE - 1)
return -EINVAL;
data = memdup_user_nul(buf, count);
@@ -1834,6 +1834,10 @@ static ssize_t smk_write_ambient(struct
if (!smack_privileged(CAP_MAC_ADMIN))
return -EPERM;
+ /* Enough data must be present */
+ if (count == 0 || count > PAGE_SIZE)
+ return -EINVAL;
+
data = memdup_user_nul(buf, count);
if (IS_ERR(data))
return PTR_ERR(data);
@@ -2005,6 +2009,9 @@ static ssize_t smk_write_onlycap(struct
if (!smack_privileged(CAP_MAC_ADMIN))
return -EPERM;
+ if (count > PAGE_SIZE)
+ return -EINVAL;
+
data = memdup_user_nul(buf, count);
if (IS_ERR(data))
return PTR_ERR(data);
@@ -2092,6 +2099,9 @@ static ssize_t smk_write_unconfined(stru
if (!smack_privileged(CAP_MAC_ADMIN))
return -EPERM;
+ if (count > PAGE_SIZE)
+ return -EINVAL;
+
data = memdup_user_nul(buf, count);
if (IS_ERR(data))
return PTR_ERR(data);
@@ -2648,6 +2658,10 @@ static ssize_t smk_write_syslog(struct f
if (!smack_privileged(CAP_MAC_ADMIN))
return -EPERM;
+ /* Enough data must be present */
+ if (count == 0 || count > PAGE_SIZE)
+ return -EINVAL;
+
data = memdup_user_nul(buf, count);
if (IS_ERR(data))
return PTR_ERR(data);
@@ -2740,10 +2754,13 @@ static ssize_t smk_write_relabel_self(st
return -EPERM;
/*
+ * No partial write.
* Enough data must be present.
*/
if (*ppos != 0)
return -EINVAL;
+ if (count == 0 || count > PAGE_SIZE)
+ return -EINVAL;
data = memdup_user_nul(buf, count);
if (IS_ERR(data))
Patches currently in stable-queue which might be from snovitoll@xxxxxxxxx are
queue-5.11/smackfs-restrict-bytes-count-in-smackfs-write-functions.patch
