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vfs, security: Fix automount superblock LSM init problem, preventing NFS sb sharing 

[ Upstream commit d80a8f1b58 ]

When NFS superblocks are created by automounting, their LSM parameters
aren't set in the fs_context struct prior to sget_fc() being called,
leading to failure to match existing superblocks.

This bug leads to messages like the following appearing in dmesg when
fscache is enabled:

    NFS: Cache volume key already in use (nfs,4.2,2,108,106a8c0,1,,,,100000,100000,2ee,3a98,1d4c,3a98,1)

Fix this by adding a new LSM hook to load fc->security for submount
creation.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/165962680944.3334508.6610023900349142034.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/165962729225.3357250.14350728846471527137.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/165970659095.2812394.6868894171102318796.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/166133579016.3678898.6283195019480567275.stgit@warthog.procyon.org.uk/ # v4
Link: https://lore.kernel.org/r/217595.1662033775@warthog.procyon.org.uk/ # v5
Fixes: 9bc61ab18b ("vfs: Introduce fs_context, switch vfs_kern_mount() to it.")
Fixes: 779df6a548 ("NFS: Ensure security label is set for root inode")
Tested-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Acked-by: "Christian Brauner (Microsoft)" <brauner@kernel.org>
Acked-by: Paul Moore <paul@paul-moore.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Message-Id: <20230808-master-v9-1-e0ecde888221@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
David Howells 2023-08-08 07:34:20 -04:00 committed by Greg Kroah-Hartman
parent 1cdf51b4e5
commit ed134f284b
6 changed files with 116 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
fs/fs_context.c
View File

@ -315,10 +315,31 @@ struct fs_context *fs_context_for_reconfigure(struct dentry *dentry,
}
EXPORT_SYMBOL(fs_context_for_reconfigure);
/**
* fs_context_for_submount: allocate a new fs_context for a submount
* @type: file_system_type of the new context
* @reference: reference dentry from which to copy relevant info
*
* Allocate a new fs_context suitable for a submount. This also ensures that
* the fc->security object is inherited from @reference (if needed).
*/
struct fs_context *fs_context_for_submount(struct file_system_type *type,
struct dentry *reference)
{
return alloc_fs_context(type, reference, 0, 0, FS_CONTEXT_FOR_SUBMOUNT);
struct fs_context *fc;
int ret;
fc = alloc_fs_context(type, reference, 0, 0, FS_CONTEXT_FOR_SUBMOUNT);
if (IS_ERR(fc))
return fc;
ret = security_fs_context_submount(fc, reference->d_sb);
if (ret) {
put_fs_context(fc);
return ERR_PTR(ret);
}
return fc;
}
EXPORT_SYMBOL(fs_context_for_submount);

1
include/linux/lsm_hook_defs.h
View File

@ -54,6 +54,7 @@ LSM_HOOK(int, 0, bprm_creds_from_file, struct linux_binprm *bprm, struct file *f
LSM_HOOK(int, 0, bprm_check_security, struct linux_binprm *bprm)
LSM_HOOK(void, LSM_RET_VOID, bprm_committing_creds, struct linux_binprm *bprm)
LSM_HOOK(void, LSM_RET_VOID, bprm_committed_creds, struct linux_binprm *bprm)
LSM_HOOK(int, 0, fs_context_submount, struct fs_context *fc, struct super_block *reference)
LSM_HOOK(int, 0, fs_context_dup, struct fs_context *fc,
struct fs_context *src_sc)
LSM_HOOK(int, -ENOPARAM, fs_context_parse_param, struct fs_context *fc,

6
include/linux/security.h
View File

@ -293,6 +293,7 @@ int security_bprm_creds_from_file(struct linux_binprm *bprm, struct file *file);
int security_bprm_check(struct linux_binprm *bprm);
void security_bprm_committing_creds(struct linux_binprm *bprm);
void security_bprm_committed_creds(struct linux_binprm *bprm);
int security_fs_context_submount(struct fs_context *fc, struct super_block *reference);
int security_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc);
int security_fs_context_parse_param(struct fs_context *fc, struct fs_parameter *param);
int security_sb_alloc(struct super_block *sb);
@ -625,6 +626,11 @@ static inline void security_bprm_committed_creds(struct linux_binprm *bprm)
{
}
static inline int security_fs_context_submount(struct fs_context *fc,
struct super_block *reference)
{
return 0;
}
static inline int security_fs_context_dup(struct fs_context *fc,
struct fs_context *src_fc)
{

14
security/security.c
View File

@ -882,6 +882,20 @@ void security_bprm_committed_creds(struct linux_binprm *bprm)
call_void_hook(bprm_committed_creds, bprm);
}
/**
* security_fs_context_submount() - Initialise fc->security
* @fc: new filesystem context
* @reference: dentry reference for submount/remount
*
* Fill out the ->security field for a new fs_context.
*
* Return: Returns 0 on success or negative error code on failure.
*/
int security_fs_context_submount(struct fs_context *fc, struct super_block *reference)
{
return call_int_hook(fs_context_submount, 0, fc, reference);
}
int security_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc)
{
return call_int_hook(fs_context_dup, 0, fc, src_fc);

22
security/selinux/hooks.c
View File

@ -2766,6 +2766,27 @@ static int selinux_umount(struct vfsmount *mnt, int flags)
FILESYSTEM__UNMOUNT, NULL);
}
static int selinux_fs_context_submount(struct fs_context *fc,
struct super_block *reference)
{
const struct superblock_security_struct *sbsec;
struct selinux_mnt_opts *opts;
opts = kzalloc(sizeof(*opts), GFP_KERNEL);
if (!opts)
return -ENOMEM;
sbsec = selinux_superblock(reference);
if (sbsec->flags & FSCONTEXT_MNT)
opts->fscontext_sid = sbsec->sid;
if (sbsec->flags & CONTEXT_MNT)
opts->context_sid = sbsec->mntpoint_sid;
if (sbsec->flags & DEFCONTEXT_MNT)
opts->defcontext_sid = sbsec->def_sid;
fc->security = opts;
return 0;
}
static int selinux_fs_context_dup(struct fs_context *fc,
struct fs_context *src_fc)
{
@ -7263,6 +7284,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
/*
* PUT "CLONING" (ACCESSING + ALLOCATING) HOOKS HERE
*/
LSM_HOOK_INIT(fs_context_submount, selinux_fs_context_submount),
LSM_HOOK_INIT(fs_context_dup, selinux_fs_context_dup),
LSM_HOOK_INIT(fs_context_parse_param, selinux_fs_context_parse_param),
LSM_HOOK_INIT(sb_eat_lsm_opts, selinux_sb_eat_lsm_opts),

51
security/smack/smack_lsm.c
View File

@ -611,6 +611,56 @@ out_opt_err:
return -EINVAL;
}
/**
* smack_fs_context_submount - Initialise security data for a filesystem context
* @fc: The filesystem context.
* @reference: reference superblock
*
* Returns 0 on success or -ENOMEM on error.
*/
static int smack_fs_context_submount(struct fs_context *fc,
struct super_block *reference)
{
struct superblock_smack *sbsp;
struct smack_mnt_opts *ctx;
struct inode_smack *isp;
ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
if (!ctx)
return -ENOMEM;
fc->security = ctx;
sbsp = smack_superblock(reference);
isp = smack_inode(reference->s_root->d_inode);
if (sbsp->smk_default) {
ctx->fsdefault = kstrdup(sbsp->smk_default->smk_known, GFP_KERNEL);
if (!ctx->fsdefault)
return -ENOMEM;
}
if (sbsp->smk_floor) {
ctx->fsfloor = kstrdup(sbsp->smk_floor->smk_known, GFP_KERNEL);
if (!ctx->fsfloor)
return -ENOMEM;
}
if (sbsp->smk_hat) {
ctx->fshat = kstrdup(sbsp->smk_hat->smk_known, GFP_KERNEL);
if (!ctx->fshat)
return -ENOMEM;
}
if (isp->smk_flags & SMK_INODE_TRANSMUTE) {
if (sbsp->smk_root) {
ctx->fstransmute = kstrdup(sbsp->smk_root->smk_known, GFP_KERNEL);
if (!ctx->fstransmute)
return -ENOMEM;
}
}
return 0;
}
/**
* smack_fs_context_dup - Duplicate the security data on fs_context duplication
* @fc: The new filesystem context.
@ -4792,6 +4842,7 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(ptrace_traceme, smack_ptrace_traceme),
LSM_HOOK_INIT(syslog, smack_syslog),
LSM_HOOK_INIT(fs_context_submount, smack_fs_context_submount),
LSM_HOOK_INIT(fs_context_dup, smack_fs_context_dup),
LSM_HOOK_INIT(fs_context_parse_param, smack_fs_context_parse_param),