From: Max Kellermann <max.kellermann@ionos.com> stable inclusion from stable-v6.6.74 commit 933689000dff37b855a8d4ffc67d3c43ed8a17e4 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IC9PNO Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit e5a8b6446c0d370716f193771ccacf3260a57534 ] Instead of storing an opaque string, call security_secctx_to_secid() right in the "secctx" command handler and store only the numeric "secid". This eliminates an unnecessary string allocation and allows the daemon to receive errors when writing the "secctx" command instead of postponing the error to the "bind" command handler. For example, if the kernel was built without `CONFIG_SECURITY`, "bind" will return `EOPNOTSUPP`, but the daemon doesn't know why. With this patch, the "secctx" will instead return `EOPNOTSUPP` which is the right context for this error. This patch adds a boolean flag `have_secid` because I'm not sure if we can safely assume that zero is the special secid value for "not set". This appears to be true for SELinux, Smack and AppArmor, but since this attribute is not documented, I'm unable to derive a stable guarantee for that. Signed-off-by: Max Kellermann <max.kellermann@ionos.com> Signed-off-by: David Howells <dhowells@redhat.com> Link: https://lore.kernel.org/r/20241209141554.638708-1-max.kellermann@ionos.com/ Link: https://lore.kernel.org/r/20241213135013.2964079-6-dhowells@redhat.com Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Conflicts: fs/cachefiles/daemon.c [Different error codes do not affect the patch.] Signed-off-by: Zizhi Wo <wozizhi@huawei.com> --- fs/cachefiles/daemon.c | 14 +++++++------- fs/cachefiles/internal.h | 3 ++- fs/cachefiles/security.c | 6 +++--- 3 files changed, 12 insertions(+), 11 deletions(-) diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c index 81d12106ce7a..32c14f0ce776 100644 --- a/fs/cachefiles/daemon.c +++ b/fs/cachefiles/daemon.c @@ -15,6 +15,7 @@ #include <linux/namei.h> #include <linux/poll.h> #include <linux/mount.h> +#include <linux/security.h> #include <linux/statfs.h> #include <linux/ctype.h> #include <linux/string.h> @@ -576,7 +577,7 @@ static int cachefiles_daemon_dir(struct cachefiles_cache *cache, char *args) */ static int cachefiles_daemon_secctx(struct cachefiles_cache *cache, char *args) { - char *secctx; + int err; _enter(",%s", args); @@ -585,16 +586,16 @@ static int cachefiles_daemon_secctx(struct cachefiles_cache *cache, char *args) return -EINVAL; } - if (cache->secctx) { + if (cache->have_secid) { pr_err("Second security context specified\n"); return -EEXIST; } - secctx = kstrdup(args, GFP_KERNEL); - if (!secctx) - return -ENOMEM; + err = security_secctx_to_secid(args, strlen(args), &cache->secid); + if (err) + return err; - cache->secctx = secctx; + cache->have_secid = true; return 0; } @@ -830,7 +831,6 @@ static void cachefiles_daemon_unbind(struct cachefiles_cache *cache) put_cred(cache->cache_cred); kfree(cache->rootdirname); - kfree(cache->secctx); kfree(cache->tag); _leave(""); diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h index 7215e96fc2cf..5ca4ab010a0a 100644 --- a/fs/cachefiles/internal.h +++ b/fs/cachefiles/internal.h @@ -125,7 +125,6 @@ struct cachefiles_cache { #define CACHEFILES_STATE_CHANGED 3 /* T if state changed (poll trigger) */ #define CACHEFILES_ONDEMAND_MODE 4 /* T if in on-demand read mode */ char *rootdirname; /* name of cache root directory */ - char *secctx; /* LSM security context */ char *tag; /* cache binding tag */ refcount_t unbind_pincount;/* refcount to do daemon unbind */ struct xarray reqs; /* xarray of pending on-demand requests */ @@ -133,6 +132,8 @@ struct cachefiles_cache { struct xarray ondemand_ids; /* xarray for ondemand_id allocation */ u32 ondemand_id_next; u32 msg_id_next; + u32 secid; /* LSM security id */ + bool have_secid; /* whether "secid" was set */ }; static inline bool cachefiles_in_ondemand_mode(struct cachefiles_cache *cache) diff --git a/fs/cachefiles/security.c b/fs/cachefiles/security.c index fe777164f1d8..fc6611886b3b 100644 --- a/fs/cachefiles/security.c +++ b/fs/cachefiles/security.c @@ -18,7 +18,7 @@ int cachefiles_get_security_ID(struct cachefiles_cache *cache) struct cred *new; int ret; - _enter("{%s}", cache->secctx); + _enter("{%u}", cache->have_secid ? cache->secid : 0); new = prepare_kernel_cred(current); if (!new) { @@ -26,8 +26,8 @@ int cachefiles_get_security_ID(struct cachefiles_cache *cache) goto error; } - if (cache->secctx) { - ret = set_security_override_from_ctx(new, cache->secctx); + if (cache->have_secid) { + ret = set_security_override(new, cache->secid); if (ret < 0) { put_cred(new); pr_err("Security denies permission to nominate security context: error %d\n", -- 2.39.2