[apparmor] [PATCH 3/7] apparmor: Convert from sb_mount to granular mount hooks
Song Liu
song at kernel.org
Wed Mar 18 18:43:56 UTC 2026
Replace AppArmor's monolithic apparmor_sb_mount() with granular
mount hooks.
Key changes:
- mount_bind: uses the pre-resolved struct path from VFS instead of
re-resolving dev_name via kern_path(), eliminating a TOCTOU
vulnerability. aa_bind_mount() now takes a struct path instead of
a string for the source.
- mount_new, mount_remount: receive the original mount(2) flags and
data parameters for policy matching via match_mnt_flags() and
AA_MNT_CONT_MATCH data matching.
- mount_reconfigure: handles MS_REMOUNT|MS_BIND (mount attribute
reconfiguration) which was previously handled as a remount.
- mount_move: reuses apparmor_move_mount() which already handles
pre-resolved paths.
- mount_change_type: propagation type changes.
aa_move_mount_old() is removed since move mounts now go through
security_mount_move() with pre-resolved struct path pointers for
both the old mount(2) and new move_mount(2) APIs.
Code generated with the assistance of Claude, reviewed by human.
Signed-off-by: Song Liu <song at kernel.org>
---
security/apparmor/include/mount.h | 5 +-
security/apparmor/lsm.c | 99 ++++++++++++++++++++++++-------
security/apparmor/mount.c | 37 ++----------
3 files changed, 83 insertions(+), 58 deletions(-)
diff --git a/security/apparmor/include/mount.h b/security/apparmor/include/mount.h
index 46834f828179..088e2f938cc1 100644
--- a/security/apparmor/include/mount.h
+++ b/security/apparmor/include/mount.h
@@ -31,16 +31,13 @@ int aa_remount(const struct cred *subj_cred,
int aa_bind_mount(const struct cred *subj_cred,
struct aa_label *label, const struct path *path,
- const char *old_name, unsigned long flags);
+ const struct path *old_path, bool recurse);
int aa_mount_change_type(const struct cred *subj_cred,
struct aa_label *label, const struct path *path,
unsigned long flags);
-int aa_move_mount_old(const struct cred *subj_cred,
- struct aa_label *label, const struct path *path,
- const char *old_name);
int aa_move_mount(const struct cred *subj_cred,
struct aa_label *label, const struct path *from_path,
const struct path *to_path);
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 48a8655af11e..7fe774535992 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -13,6 +13,7 @@
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/mount.h>
+#include <linux/fs_context.h>
#include <linux/namei.h>
#include <linux/ptrace.h>
#include <linux/ctype.h>
@@ -697,34 +698,83 @@ static int apparmor_uring_sqpoll(void)
}
#endif /* CONFIG_IO_URING */
-static int apparmor_sb_mount(const char *dev_name, const struct path *path,
- const char *type, unsigned long flags, void *data)
+static int apparmor_mount_bind(const struct path *from, const struct path *to,
+ bool recurse)
{
struct aa_label *label;
int error = 0;
bool needput;
- flags &= ~AA_MS_IGNORE_MASK;
+ label = __begin_current_label_crit_section(&needput);
+ if (!unconfined(label))
+ error = aa_bind_mount(current_cred(), label, to, from,
+ recurse);
+ __end_current_label_crit_section(label, needput);
+ return error;
+}
+
+static int apparmor_mount_new(struct fs_context *fc, const struct path *mp,
+ int mnt_flags, unsigned long flags, void *data)
+{
+ struct aa_label *label;
+ int error = 0;
+ bool needput;
+
+ /* flags and data are from the original mount(2) call */
label = __begin_current_label_crit_section(&needput);
- if (!unconfined(label)) {
- if (flags & MS_REMOUNT)
- error = aa_remount(current_cred(), label, path, flags,
- data);
- else if (flags & MS_BIND)
- error = aa_bind_mount(current_cred(), label, path,
- dev_name, flags);
- else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE |
- MS_UNBINDABLE))
- error = aa_mount_change_type(current_cred(), label,
- path, flags);
- else if (flags & MS_MOVE)
- error = aa_move_mount_old(current_cred(), label, path,
- dev_name);
- else
- error = aa_new_mount(current_cred(), label, dev_name,
- path, type, flags, data);
- }
+ if (!unconfined(label))
+ error = aa_new_mount(current_cred(), label, fc->source,
+ mp, fc->fs_type->name, flags, data);
+ __end_current_label_crit_section(label, needput);
+
+ return error;
+}
+
+static int apparmor_mount_remount(struct fs_context *fc, const struct path *mp,
+ int mnt_flags, unsigned long flags,
+ void *data)
+{
+ struct aa_label *label;
+ int error = 0;
+ bool needput;
+
+ /* flags and data are from the original mount(2) call */
+ label = __begin_current_label_crit_section(&needput);
+ if (!unconfined(label))
+ error = aa_remount(current_cred(), label, mp, flags, data);
+ __end_current_label_crit_section(label, needput);
+
+ return error;
+}
+
+static int apparmor_mount_reconfigure(const struct path *mp,
+ unsigned int mnt_flags,
+ unsigned long flags)
+{
+ struct aa_label *label;
+ int error = 0;
+ bool needput;
+
+ /* flags are from the original mount(2) call */
+ label = __begin_current_label_crit_section(&needput);
+ if (!unconfined(label))
+ error = aa_remount(current_cred(), label, mp, flags, NULL);
+ __end_current_label_crit_section(label, needput);
+
+ return error;
+}
+
+static int apparmor_mount_change_type(const struct path *mp, int ms_flags)
+{
+ struct aa_label *label;
+ int error = 0;
+ bool needput;
+
+ label = __begin_current_label_crit_section(&needput);
+ if (!unconfined(label))
+ error = aa_mount_change_type(current_cred(), label, mp,
+ ms_flags);
__end_current_label_crit_section(label, needput);
return error;
@@ -1664,7 +1714,12 @@ static struct security_hook_list apparmor_hooks[] __ro_after_init = {
LSM_HOOK_INIT(capable, apparmor_capable),
LSM_HOOK_INIT(move_mount, apparmor_move_mount),
- LSM_HOOK_INIT(sb_mount, apparmor_sb_mount),
+ LSM_HOOK_INIT(mount_bind, apparmor_mount_bind),
+ LSM_HOOK_INIT(mount_new, apparmor_mount_new),
+ LSM_HOOK_INIT(mount_remount, apparmor_mount_remount),
+ LSM_HOOK_INIT(mount_reconfigure, apparmor_mount_reconfigure),
+ LSM_HOOK_INIT(mount_move, apparmor_move_mount),
+ LSM_HOOK_INIT(mount_change_type, apparmor_mount_change_type),
LSM_HOOK_INIT(sb_umount, apparmor_sb_umount),
LSM_HOOK_INIT(sb_pivotroot, apparmor_sb_pivotroot),
diff --git a/security/apparmor/mount.c b/security/apparmor/mount.c
index 523570aa1a5a..38b40e16014f 100644
--- a/security/apparmor/mount.c
+++ b/security/apparmor/mount.c
@@ -418,25 +418,17 @@ int aa_remount(const struct cred *subj_cred,
}
int aa_bind_mount(const struct cred *subj_cred,
- struct aa_label *label, const struct path *path,
- const char *dev_name, unsigned long flags)
+ struct aa_label *label, const struct path *path,
+ const struct path *old_path, bool recurse)
{
struct aa_profile *profile;
char *buffer = NULL, *old_buffer = NULL;
- struct path old_path;
+ unsigned long flags = MS_BIND | (recurse ? MS_REC : 0);
int error;
AA_BUG(!label);
AA_BUG(!path);
-
- if (!dev_name || !*dev_name)
- return -EINVAL;
-
- flags &= MS_REC | MS_BIND;
-
- error = kern_path(dev_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
- if (error)
- return error;
+ AA_BUG(!old_path);
buffer = aa_get_buffer(false);
old_buffer = aa_get_buffer(false);
@@ -445,12 +437,11 @@ int aa_bind_mount(const struct cred *subj_cred,
goto out;
error = fn_for_each_confined(label, profile,
- match_mnt(subj_cred, profile, path, buffer, &old_path,
+ match_mnt(subj_cred, profile, path, buffer, old_path,
old_buffer, NULL, flags, NULL, false));
out:
aa_put_buffer(buffer);
aa_put_buffer(old_buffer);
- path_put(&old_path);
return error;
}
@@ -514,24 +505,6 @@ int aa_move_mount(const struct cred *subj_cred,
return error;
}
-int aa_move_mount_old(const struct cred *subj_cred, struct aa_label *label,
- const struct path *path, const char *orig_name)
-{
- struct path old_path;
- int error;
-
- if (!orig_name || !*orig_name)
- return -EINVAL;
- error = kern_path(orig_name, LOOKUP_FOLLOW, &old_path);
- if (error)
- return error;
-
- error = aa_move_mount(subj_cred, label, &old_path, path);
- path_put(&old_path);
-
- return error;
-}
-
int aa_new_mount(const struct cred *subj_cred, struct aa_label *label,
const char *dev_name, const struct path *path,
const char *type, unsigned long flags, void *data)
--
2.52.0
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