From 2097f59920ea81516d7783396683cad22c26d140 Mon Sep 17 00:00:00 2001 From: Himanshu Shukla Date: Thu, 10 Nov 2016 16:19:52 +0530 Subject: [PATCH] smack: parse mnt opts after privileges check In smack_set_mnt_opts()first the SMACK mount options are being parsed and later it is being checked whether the user calling mount has CAP_MAC_ADMIN capability. This sequence of operationis will allow unauthorized user to add SMACK labels in label list and may cause denial of security attack by adding many labels by allocating kernel memory by unauthorized user. Superblock smack flag is also being set as initialized though function may return with EPERM error. First check the capability of calling user then set the SMACK attributes and smk_flags. Signed-off-by: Himanshu Shukla Acked-by: Casey Schaufler --- security/smack/smack_lsm.c | 50 +++++++++++++++++++------------------- 1 file changed, 25 insertions(+), 25 deletions(-) diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index e73460d5acc6..788a5faf3774 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -769,6 +769,31 @@ static int smack_set_mnt_opts(struct super_block *sb, if (sp->smk_flags & SMK_SB_INITIALIZED) return 0; + if (!smack_privileged(CAP_MAC_ADMIN)) { + /* + * Unprivileged mounts don't get to specify Smack values. + */ + if (num_opts) + return -EPERM; + /* + * Unprivileged mounts get root and default from the caller. + */ + skp = smk_of_current(); + sp->smk_root = skp; + sp->smk_default = skp; + /* + * For a handful of fs types with no user-controlled + * backing store it's okay to trust security labels + * in the filesystem. The rest are untrusted. + */ + if (sb->s_user_ns != &init_user_ns && + sb->s_magic != SYSFS_MAGIC && sb->s_magic != TMPFS_MAGIC && + sb->s_magic != RAMFS_MAGIC) { + transmute = 1; + sp->smk_flags |= SMK_SB_UNTRUSTED; + } + } + sp->smk_flags |= SMK_SB_INITIALIZED; for (i = 0; i < num_opts; i++) { @@ -809,31 +834,6 @@ static int smack_set_mnt_opts(struct super_block *sb, } } - if (!smack_privileged(CAP_MAC_ADMIN)) { - /* - * Unprivileged mounts don't get to specify Smack values. - */ - if (num_opts) - return -EPERM; - /* - * Unprivileged mounts get root and default from the caller. - */ - skp = smk_of_current(); - sp->smk_root = skp; - sp->smk_default = skp; - /* - * For a handful of fs types with no user-controlled - * backing store it's okay to trust security labels - * in the filesystem. The rest are untrusted. - */ - if (sb->s_user_ns != &init_user_ns && - sb->s_magic != SYSFS_MAGIC && sb->s_magic != TMPFS_MAGIC && - sb->s_magic != RAMFS_MAGIC) { - transmute = 1; - sp->smk_flags |= SMK_SB_UNTRUSTED; - } - } - /* * Initialize the root inode. */ -- 2.20.1