From 1dd671e7c8b4ff696b3df544fad41d0ddbbfc5a0 Mon Sep 17 00:00:00 2001 From: Scott Mayhew Date: Wed, 28 Aug 2024 15:51:29 -0400 Subject: [PATCH] selinux,smack: don't bypass permissions check in inode_setsecctx hook BugLink: https://bugs.launchpad.net/bugs/2084225 commit 76a0e79bc84f466999fa501fce5bf7a07641b8a7 upstream. Marek Gresko reports that the root user on an NFS client is able to change the security labels on files on an NFS filesystem that is exported with root squashing enabled. The end of the kerneldoc comment for __vfs_setxattr_noperm() states: * This function requires the caller to lock the inode's i_mutex before it * is executed. It also assumes that the caller will make the appropriate * permission checks. nfsd_setattr() does do permissions checking via fh_verify() and nfsd_permission(), but those don't do all the same permissions checks that are done by security_inode_setxattr() and its related LSM hooks do. Since nfsd_setattr() is the only consumer of security_inode_setsecctx(), simplest solution appears to be to replace the call to __vfs_setxattr_noperm() with a call to __vfs_setxattr_locked(). This fixes the above issue and has the added benefit of causing nfsd to recall conflicting delegations on a file when a client tries to change its security label. Cc: stable@kernel.org Reported-by: Marek Gresko Link: https://bugzilla.kernel.org/show_bug.cgi?id=218809 Signed-off-by: Scott Mayhew Tested-by: Stephen Smalley Reviewed-by: Stephen Smalley Reviewed-by: Chuck Lever Reviewed-by: Jeff Layton Acked-by: Casey Schaufler Signed-off-by: Paul Moore Signed-off-by: Greg Kroah-Hartman Signed-off-by: Koichiro Den Signed-off-by: Stefan Bader --- security/selinux/hooks.c | 4 ++-- security/smack/smack_lsm.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 0e98207ad0d6..35e763fa6aa5 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -6709,8 +6709,8 @@ static int selinux_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen */ static int selinux_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen) { - return __vfs_setxattr_noperm(&nop_mnt_idmap, dentry, XATTR_NAME_SELINUX, - ctx, ctxlen, 0); + return __vfs_setxattr_locked(&nop_mnt_idmap, dentry, XATTR_NAME_SELINUX, + ctx, ctxlen, 0, NULL); } static int selinux_inode_getsecctx(struct inode *inode, struct lsmcontext *cp) diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index 4fb9f3e76d44..2fb54398ff19 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -4911,8 +4911,8 @@ static int smack_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen) static int smack_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen) { - return __vfs_setxattr_noperm(&nop_mnt_idmap, dentry, XATTR_NAME_SMACK, - ctx, ctxlen, 0); + return __vfs_setxattr_locked(&nop_mnt_idmap, dentry, XATTR_NAME_SMACK, + ctx, ctxlen, 0, NULL); } static int smack_inode_getsecctx(struct inode *inode, struct lsmcontext *cp)