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apparmor: make __begin_current_label_crit_section() indicate whether put is needed

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Same as aa_get_newest_cred_label_condref().

This avoids a bunch of work overall and allows the compiler to note when no
clean up is necessary, allowing for tail calls.

This in particular happens in apparmor_file_permission(), which manages to
tail call aa_file_perm() 105 bytes in (vs a regular call 112 bytes in
followed by branches to figure out if clean up is needed).

Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
This commit is contained in:
Mateusz Guzik 2025-03-18 23:06:41 +01:00 • committed by John Johansen
parent 37a3741d27
commit 87cc7b0011
3 changed files with 67 additions and 41 deletions
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21
security/apparmor/include/cred.h
View file

@ -114,7 +114,12 @@ static inline struct aa_label *aa_get_current_label(void)
return aa_get_label(l);
}
#define __end_current_label_crit_section(X) end_current_label_crit_section(X)
static inline void __end_current_label_crit_section(struct aa_label *label,
bool needput)
{
if (unlikely(needput))
aa_put_label(label);
}
/**
* end_current_label_crit_section - put a reference found with begin_current_label..
@ -142,13 +147,16 @@ static inline void end_current_label_crit_section(struct aa_label *label)
* critical section between __begin_current_label_crit_section() ..
* __end_current_label_crit_section()
*/
static inline struct aa_label *__begin_current_label_crit_section(void)
static inline struct aa_label *__begin_current_label_crit_section(bool *needput)
{
struct aa_label *label = aa_current_raw_label();
if (label_is_stale(label))
label = aa_get_newest_label(label);
if (label_is_stale(label)) {
*needput = true;
return aa_get_newest_label(label);
}
*needput = false;
return label;
}
@ -184,10 +192,11 @@ static inline struct aa_ns *aa_get_current_ns(void)
{
struct aa_label *label;
struct aa_ns *ns;
bool needput;
label = __begin_current_label_crit_section();
label = __begin_current_label_crit_section(&needput);
ns = aa_get_ns(labels_ns(label));
__end_current_label_crit_section(label);
__end_current_label_crit_section(label, needput);
return ns;
}

75
security/apparmor/lsm.c
View file

@ -127,14 +127,15 @@ static int apparmor_ptrace_access_check(struct task_struct *child,
struct aa_label *tracer, *tracee;
const struct cred *cred;
int error;
bool needput;
cred = get_task_cred(child);
tracee = cred_label(cred); /* ref count on cred */
tracer = __begin_current_label_crit_section();
tracer = __begin_current_label_crit_section(&needput);
error = aa_may_ptrace(current_cred(), tracer, cred, tracee,
(mode & PTRACE_MODE_READ) ? AA_PTRACE_READ
: AA_PTRACE_TRACE);
__end_current_label_crit_section(tracer);
__end_current_label_crit_section(tracer, needput);
put_cred(cred);
return error;
@ -145,14 +146,15 @@ static int apparmor_ptrace_traceme(struct task_struct *parent)
struct aa_label *tracer, *tracee;
const struct cred *cred;
int error;
bool needput;
tracee = __begin_current_label_crit_section();
tracee = __begin_current_label_crit_section(&needput);
cred = get_task_cred(parent);
tracer = cred_label(cred); /* ref count on cred */
error = aa_may_ptrace(cred, tracer, current_cred(), tracee,
AA_PTRACE_TRACE);
put_cred(cred);
__end_current_label_crit_section(tracee);
__end_current_label_crit_section(tracee, needput);
return error;
}
@ -221,12 +223,13 @@ static int common_perm(const char *op, const struct path *path, u32 mask,
{
struct aa_label *label;
int error = 0;
bool needput;
label = __begin_current_label_crit_section();
label = __begin_current_label_crit_section(&needput);
if (!unconfined(label))
error = aa_path_perm(op, current_cred(), label, path, 0, mask,
cond);
__end_current_label_crit_section(label);
__end_current_label_crit_section(label, needput);
return error;
}
@ -524,14 +527,15 @@ static int common_file_perm(const char *op, struct file *file, u32 mask,
{
struct aa_label *label;
int error = 0;
bool needput;
/* don't reaudit files closed during inheritance */
if (file->f_path.dentry == aa_null.dentry)
if (unlikely(file->f_path.dentry == aa_null.dentry))
return -EACCES;
label = __begin_current_label_crit_section();
label = __begin_current_label_crit_section(&needput);
error = aa_file_perm(op, current_cred(), label, file, mask, in_atomic);
__end_current_label_crit_section(label);
__end_current_label_crit_section(label, needput);
return error;
}
@ -664,15 +668,16 @@ static int apparmor_uring_override_creds(const struct cred *new)
struct aa_profile *profile;
struct aa_label *label;
int error;
bool needput;
DEFINE_AUDIT_DATA(ad, LSM_AUDIT_DATA_NONE, AA_CLASS_IO_URING,
OP_URING_OVERRIDE);
ad.uring.target = cred_label(new);
label = __begin_current_label_crit_section();
label = __begin_current_label_crit_section(&needput);
error = fn_for_each(label, profile,
profile_uring(profile, AA_MAY_OVERRIDE_CRED,
cred_label(new), CAP_SYS_ADMIN, &ad));
__end_current_label_crit_section(label);
__end_current_label_crit_section(label, needput);
return error;
}
@ -688,14 +693,15 @@ static int apparmor_uring_sqpoll(void)
struct aa_profile *profile;
struct aa_label *label;
int error;
bool needput;
DEFINE_AUDIT_DATA(ad, LSM_AUDIT_DATA_NONE, AA_CLASS_IO_URING,
OP_URING_SQPOLL);
label = __begin_current_label_crit_section();
label = __begin_current_label_crit_section(&needput);
error = fn_for_each(label, profile,
profile_uring(profile, AA_MAY_CREATE_SQPOLL,
NULL, CAP_SYS_ADMIN, &ad));
__end_current_label_crit_section(label);
__end_current_label_crit_section(label, needput);
return error;
}
@ -706,6 +712,7 @@ static int apparmor_sb_mount(const char *dev_name, const struct path *path,
{
struct aa_label *label;
int error = 0;
bool needput;
/* Discard magic */
if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
@ -713,7 +720,7 @@ static int apparmor_sb_mount(const char *dev_name, const struct path *path,
flags &= ~AA_MS_IGNORE_MASK;
label = __begin_current_label_crit_section();
label = __begin_current_label_crit_section(&needput);
if (!unconfined(label)) {
if (flags & MS_REMOUNT)
error = aa_remount(current_cred(), label, path, flags,
@ -732,7 +739,7 @@ static int apparmor_sb_mount(const char *dev_name, const struct path *path,
error = aa_new_mount(current_cred(), label, dev_name,
path, type, flags, data);
}
__end_current_label_crit_section(label);
__end_current_label_crit_section(label, needput);
return error;
}
@ -742,12 +749,13 @@ static int apparmor_move_mount(const struct path *from_path,
{
struct aa_label *label;
int error = 0;
bool needput;
label = __begin_current_label_crit_section();
label = __begin_current_label_crit_section(&needput);
if (!unconfined(label))
error = aa_move_mount(current_cred(), label, from_path,
to_path);
__end_current_label_crit_section(label);
__end_current_label_crit_section(label, needput);
return error;
}
@ -756,11 +764,12 @@ static int apparmor_sb_umount(struct vfsmount *mnt, int flags)
{
struct aa_label *label;
int error = 0;
bool needput;
label = __begin_current_label_crit_section();
label = __begin_current_label_crit_section(&needput);
if (!unconfined(label))
error = aa_umount(current_cred(), label, mnt, flags);
__end_current_label_crit_section(label);
__end_current_label_crit_section(label, needput);
return error;
}
@ -984,10 +993,12 @@ static void apparmor_bprm_committed_creds(const struct linux_binprm *bprm)
static void apparmor_current_getlsmprop_subj(struct lsm_prop *prop)
{
struct aa_label *label = __begin_current_label_crit_section();
struct aa_label *label;
bool needput;
label = __begin_current_label_crit_section(&needput);
prop->apparmor.label = label;
__end_current_label_crit_section(label);
__end_current_label_crit_section(label, needput);
}
static void apparmor_task_getlsmprop_obj(struct task_struct *p,
@ -1002,13 +1013,16 @@ static void apparmor_task_getlsmprop_obj(struct task_struct *p,
static int apparmor_task_setrlimit(struct task_struct *task,
unsigned int resource, struct rlimit *new_rlim)
{
struct aa_label *label = __begin_current_label_crit_section();
struct aa_label *label;
int error = 0;
bool needput;
label = __begin_current_label_crit_section(&needput);
if (!unconfined(label))
error = aa_task_setrlimit(current_cred(), label, task,
resource, new_rlim);
__end_current_label_crit_section(label);
__end_current_label_crit_section(label, needput);
return error;
}
@ -1019,6 +1033,7 @@ static int apparmor_task_kill(struct task_struct *target, struct kernel_siginfo
const struct cred *tc;
struct aa_label *cl, *tl;
int error;
bool needput;
tc = get_task_cred(target);
tl = aa_get_newest_cred_label(tc);
@ -1030,9 +1045,9 @@ static int apparmor_task_kill(struct task_struct *target, struct kernel_siginfo
error = aa_may_signal(cred, cl, tc, tl, sig);
aa_put_label(cl);
} else {
cl = __begin_current_label_crit_section();
cl = __begin_current_label_crit_section(&needput);
error = aa_may_signal(current_cred(), cl, tc, tl, sig);
__end_current_label_crit_section(cl);
__end_current_label_crit_section(cl, needput);
}
aa_put_label(tl);
put_cred(tc);
@ -1133,10 +1148,11 @@ static int apparmor_unix_stream_connect(struct sock *sk, struct sock *peer_sk,
struct aa_sk_ctx *new_ctx = aa_sock(newsk);
struct aa_label *label;
int error;
bool needput;
label = __begin_current_label_crit_section();
label = __begin_current_label_crit_section(&needput);
error = unix_connect_perm(current_cred(), label, sk, peer_sk);
__end_current_label_crit_section(label);
__end_current_label_crit_section(label, needput);
if (error)
return error;
@ -1163,8 +1179,9 @@ static int apparmor_unix_may_send(struct socket *sock, struct socket *peer)
struct aa_sk_ctx *peer_ctx = aa_sock(peer->sk);
struct aa_label *label;
int error;
bool needput;
label = __begin_current_label_crit_section();
label = __begin_current_label_crit_section(&needput);
error = xcheck(aa_unix_peer_perm(current_cred(),
label, OP_SENDMSG, AA_MAY_SEND,
sock->sk, peer->sk, NULL),
@ -1172,7 +1189,7 @@ static int apparmor_unix_may_send(struct socket *sock, struct socket *peer)
peer_ctx->label, OP_SENDMSG,
AA_MAY_RECEIVE,
peer->sk, sock->sk, label));
__end_current_label_crit_section(label);
__end_current_label_crit_section(label, needput);
return error;
}

12
security/apparmor/policy.c
View file

@ -870,11 +870,11 @@ bool aa_policy_admin_capable(const struct cred *subj_cred,
bool aa_current_policy_view_capable(struct aa_ns *ns)
{
struct aa_label *label;
bool res;
bool needput, res;
label = __begin_current_label_crit_section();
label = __begin_current_label_crit_section(&needput);
res = aa_policy_view_capable(current_cred(), label, ns);
__end_current_label_crit_section(label);
__end_current_label_crit_section(label, needput);
return res;
}
@ -882,11 +882,11 @@ bool aa_current_policy_view_capable(struct aa_ns *ns)
bool aa_current_policy_admin_capable(struct aa_ns *ns)
{
struct aa_label *label;
bool res;
bool needput, res;
label = __begin_current_label_crit_section();
label = __begin_current_label_crit_section(&needput);
res = aa_policy_admin_capable(current_cred(), label, ns);
__end_current_label_crit_section(label);
__end_current_label_crit_section(label, needput);
return res;
}