diff options
author | John Johansen <john.johansen@canonical.com> | 2020-01-02 05:31:22 -0800 |
---|---|---|
committer | John Johansen <john.johansen@canonical.com> | 2020-01-04 15:56:44 -0800 |
commit | 8c62ed27a12c00e3db1c9f04bc0f272bdbb06734 (patch) | |
tree | 7bbe5954a3d15944b17e1cc732eb0f479276ffda /security/apparmor | |
parent | 20d4e80d255dd7cfecb53743bc550ebcad04549d (diff) | |
download | lwn-8c62ed27a12c00e3db1c9f04bc0f272bdbb06734.tar.gz lwn-8c62ed27a12c00e3db1c9f04bc0f272bdbb06734.zip |
apparmor: fix aa_xattrs_match() may sleep while holding a RCU lock
aa_xattrs_match() is unfortunately calling vfs_getxattr_alloc() from a
context protected by an rcu_read_lock. This can not be done as
vfs_getxattr_alloc() may sleep regardles of the gfp_t value being
passed to it.
Fix this by breaking the rcu_read_lock on the policy search when the
xattr match feature is requested and restarting the search if a policy
changes occur.
Fixes: 8e51f9087f40 ("apparmor: Add support for attaching profiles via xattr, presence and value")
Reported-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Diffstat (limited to 'security/apparmor')
-rw-r--r-- | security/apparmor/apparmorfs.c | 2 | ||||
-rw-r--r-- | security/apparmor/domain.c | 82 | ||||
-rw-r--r-- | security/apparmor/policy.c | 4 |
3 files changed, 46 insertions, 42 deletions
diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c index 09996f2552ee..47aff8700547 100644 --- a/security/apparmor/apparmorfs.c +++ b/security/apparmor/apparmorfs.c @@ -623,7 +623,7 @@ static __poll_t ns_revision_poll(struct file *file, poll_table *pt) void __aa_bump_ns_revision(struct aa_ns *ns) { - ns->revision++; + WRITE_ONCE(ns->revision, ns->revision + 1); wake_up_interruptible(&ns->wait); } diff --git a/security/apparmor/domain.c b/security/apparmor/domain.c index 9be7ccb8379e..6ceb74e0f789 100644 --- a/security/apparmor/domain.c +++ b/security/apparmor/domain.c @@ -317,6 +317,7 @@ static int aa_xattrs_match(const struct linux_binprm *bprm, if (!bprm || !profile->xattr_count) return 0; + might_sleep(); /* transition from exec match to xattr set */ state = aa_dfa_null_transition(profile->xmatch, state); @@ -361,10 +362,11 @@ out: } /** - * __attach_match_ - find an attachment match + * find_attach - do attachment search for unconfined processes * @bprm - binprm structure of transitioning task - * @name - to match against (NOT NULL) + * @ns: the current namespace (NOT NULL) * @head - profile list to walk (NOT NULL) + * @name - to match against (NOT NULL) * @info - info message if there was an error (NOT NULL) * * Do a linear search on the profiles in the list. There is a matching @@ -374,12 +376,11 @@ out: * * Requires: @head not be shared or have appropriate locks held * - * Returns: profile or NULL if no match found + * Returns: label or NULL if no match found */ -static struct aa_profile *__attach_match(const struct linux_binprm *bprm, - const char *name, - struct list_head *head, - const char **info) +static struct aa_label *find_attach(const struct linux_binprm *bprm, + struct aa_ns *ns, struct list_head *head, + const char *name, const char **info) { int candidate_len = 0, candidate_xattrs = 0; bool conflict = false; @@ -388,6 +389,8 @@ static struct aa_profile *__attach_match(const struct linux_binprm *bprm, AA_BUG(!name); AA_BUG(!head); + rcu_read_lock(); +restart: list_for_each_entry_rcu(profile, head, base.list) { if (profile->label.flags & FLAG_NULL && &profile->label == ns_unconfined(profile->ns)) @@ -413,16 +416,32 @@ static struct aa_profile *__attach_match(const struct linux_binprm *bprm, perm = dfa_user_allow(profile->xmatch, state); /* any accepting state means a valid match. */ if (perm & MAY_EXEC) { - int ret; + int ret = 0; if (count < candidate_len) continue; - ret = aa_xattrs_match(bprm, profile, state); - /* Fail matching if the xattrs don't match */ - if (ret < 0) - continue; - + if (bprm && profile->xattr_count) { + long rev = READ_ONCE(ns->revision); + + if (!aa_get_profile_not0(profile)) + goto restart; + rcu_read_unlock(); + ret = aa_xattrs_match(bprm, profile, + state); + rcu_read_lock(); + aa_put_profile(profile); + if (rev != + READ_ONCE(ns->revision)) + /* policy changed */ + goto restart; + /* + * Fail matching if the xattrs don't + * match + */ + if (ret < 0) + continue; + } /* * TODO: allow for more flexible best match * @@ -445,43 +464,28 @@ static struct aa_profile *__attach_match(const struct linux_binprm *bprm, candidate_xattrs = ret; conflict = false; } - } else if (!strcmp(profile->base.name, name)) + } else if (!strcmp(profile->base.name, name)) { /* * old exact non-re match, without conditionals such * as xattrs. no more searching required */ - return profile; + candidate = profile; + goto out; + } } - if (conflict) { - *info = "conflicting profile attachments"; + if (!candidate || conflict) { + if (conflict) + *info = "conflicting profile attachments"; + rcu_read_unlock(); return NULL; } - return candidate; -} - -/** - * find_attach - do attachment search for unconfined processes - * @bprm - binprm structure of transitioning task - * @ns: the current namespace (NOT NULL) - * @list: list to search (NOT NULL) - * @name: the executable name to match against (NOT NULL) - * @info: info message if there was an error - * - * Returns: label or NULL if no match found - */ -static struct aa_label *find_attach(const struct linux_binprm *bprm, - struct aa_ns *ns, struct list_head *list, - const char *name, const char **info) -{ - struct aa_profile *profile; - - rcu_read_lock(); - profile = aa_get_profile(__attach_match(bprm, name, list, info)); +out: + candidate = aa_get_newest_profile(candidate); rcu_read_unlock(); - return profile ? &profile->label : NULL; + return &candidate->label; } static const char *next_name(int xtype, const char *name) diff --git a/security/apparmor/policy.c b/security/apparmor/policy.c index 03104830c913..269f2f53c0b1 100644 --- a/security/apparmor/policy.c +++ b/security/apparmor/policy.c @@ -1125,8 +1125,8 @@ ssize_t aa_remove_profiles(struct aa_ns *policy_ns, struct aa_label *subj, if (!name) { /* remove namespace - can only happen if fqname[0] == ':' */ mutex_lock_nested(&ns->parent->lock, ns->level); - __aa_remove_ns(ns); __aa_bump_ns_revision(ns); + __aa_remove_ns(ns); mutex_unlock(&ns->parent->lock); } else { /* remove profile */ @@ -1138,9 +1138,9 @@ ssize_t aa_remove_profiles(struct aa_ns *policy_ns, struct aa_label *subj, goto fail_ns_lock; } name = profile->base.hname; + __aa_bump_ns_revision(ns); __remove_profile(profile); __aa_labelset_update_subtree(ns); - __aa_bump_ns_revision(ns); mutex_unlock(&ns->lock); } |