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 5.10-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-5.10 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); @@ -2647,6 +2657,10 @@ 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); @@ -2739,10 +2753,13 @@ 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-5.10/smackfs-restrict-bytes-count-in-smackfs-write-functions.patch