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Signed-off-by: Paul Moore Acked-by: Casey Schaufler Reviewed-by: Mickaël Salaün --- security/security.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/security/security.c b/security/security.c index 988483fcf153..9c63acded4ee 100644 --- a/security/security.c +++ b/security/security.c @@ -3951,8 +3951,9 @@ int security_getselfattr(unsigned int attr, struct lsm_ctx __user *uctx, continue; } if (rc == -E2BIG) { - toobig = true; + rc = 0; left = 0; + toobig = true; } else if (rc < 0) return rc; else From patchwork Tue Oct 24 21:35:28 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Paul Moore X-Patchwork-Id: 13435292 X-Patchwork-Delegate: paul@paul-moore.com Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6BA6AC25B70 for ; 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Tue, 24 Oct 2023 14:39:21 -0700 (PDT) Received: from localhost ([70.22.175.108]) by smtp.gmail.com with ESMTPSA id p5-20020a05620a132500b0076d08d5f93asm3717190qkj.60.2023.10.24.14.39.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Oct 2023 14:39:21 -0700 (PDT) From: Paul Moore To: linux-security-module@vger.kernel.org Cc: selinux@vger.kernel.org, Casey Schaufler , John Johansen , =?utf-8?q?Micka=C3=ABl_Sala?= =?utf-8?q?=C3=BCn?= Subject: [RFC PATCH 2/3] lsm: correct error codes in security_getselfattr() Date: Tue, 24 Oct 2023 17:35:28 -0400 Message-ID: <20231024213525.361332-6-paul@paul-moore.com> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231024213525.361332-4-paul@paul-moore.com> References: <20231024213525.361332-4-paul@paul-moore.com> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=863; i=paul@paul-moore.com; h=from:subject; bh=ugmNzfzXFsYvckNvX1aV6BAeCvMbabcAjQNIQgYTuco=; b=owEBbQKS/ZANAwAIAeog8tqXN4lzAcsmYgBlODijlub3W8kIgCE1sgtbxoM/CkMFXdZjbwjNM nW5DjAuiKGJAjMEAAEIAB0WIQRLQqjPB/KZ1VSXfu/qIPLalzeJcwUCZTg4owAKCRDqIPLalzeJ c8FTD/4lOcUYhpZNUihf5dlWbswCIms6JVFNXf1+CzvmYz0/RooImhZPCETqhdfR9V+Ruff9qDa MhUEMO1rAgjnY/02/tU+qSUS0yL137LR2Q2zcrR1HAfnZLQgsSidsbL2u70DCdOUvlhFr96p5b5 j7T6wNjDO5HvUt/DuUnJBhoK779Uii9zHAEJoxJvWd9uwVMRAvE3shsl32O9docivyWMh1roMgT b78VW42g21zdZxs7j2YUXud08raTVD8SYbSt3P4wbUy2rODDqclkZvn0fZc18gm08omuPY0SI+/ Nu5pxCisJ2oMgMNghjOmZthbfFKkVB+1Bs2QVFGaaSxEVIZ/GsXk2gGRG0g3AX5O+uwk1gIgbDO Q12a9/0MPdGaC7uDxXYH7y7eRMXJ73yLIZTC2uX71feSbQUJLlW2pFqPrhgMIqdCmevs9oN6fQi zEeq13PBO8wuXpn7AVY+kxyVzPrThwi+KbgbD6l7droMbDKXSs7YHZ0xNkQGRiga9XXVUmEBeN1 a95EqUE2De0B7RidRQUCZHy7kIEaxuCwY7h+gV7WaWYbFNl3wuOPYQNLN/MOWg5qOqx4z6LknUO z755PVVtrgmTcIpEb9M4EpQOw32HbsfmGrL5a4S97EksDGuPg02OBSfxA4XeBXqa7E7I12i3IGR B6CkhPqoDOLPAlw== X-Developer-Key: i=paul@paul-moore.com; a=openpgp; fpr=7100AADFAE6E6E940D2E0AD655E45A5AE8CA7C8A Precedence: bulk List-ID: We should return -EINVAL if the user specifies LSM_FLAG_SINGLE without supplying a valid lsm_ctx struct buffer. Signed-off-by: Paul Moore Acked-by: Casey Schaufler Reviewed-by: Mickaël Salaün --- security/security.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/security/security.c b/security/security.c index 9c63acded4ee..67ded406a5ea 100644 --- a/security/security.c +++ b/security/security.c @@ -3923,9 +3923,9 @@ int security_getselfattr(unsigned int attr, struct lsm_ctx __user *uctx, /* * Only flag supported is LSM_FLAG_SINGLE */ - if (flags != LSM_FLAG_SINGLE) + if (flags != LSM_FLAG_SINGLE || !uctx) return -EINVAL; - if (uctx && copy_from_user(&lctx, uctx, sizeof(lctx))) + if (copy_from_user(&lctx, uctx, sizeof(lctx))) return -EFAULT; /* * If the LSM ID isn't specified it is an error. 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a=openpgp; fpr=7100AADFAE6E6E940D2E0AD655E45A5AE8CA7C8A Precedence: bulk List-ID: While we have a lsm_fill_user_ctx() helper function designed to make life easier for LSMs which return lsm_ctx structs to userspace, we didn't include all of the buffer length safety checks and buffer padding adjustments in the helper. This led to code duplication across the different LSMs and the possibility for mistakes across the different LSM subsystems. In order to reduce code duplication and decrease the chances of silly mistakes, we're consolidating all of this code into the lsm_fill_user_ctx() helper. The buffer padding is also modified from a fixed 8-byte alignment to an alignment that matches the word length of the machine (BITS_PER_LONG / 8). Signed-off-by: Paul Moore --- include/linux/security.h | 9 ++++--- security/apparmor/lsm.c | 15 +++-------- security/security.c | 55 +++++++++++++++++++++----------------- security/selinux/hooks.c | 42 +++++++++++++++-------------- security/smack/smack_lsm.c | 23 +++++----------- 5 files changed, 67 insertions(+), 77 deletions(-) diff --git a/include/linux/security.h b/include/linux/security.h index 334f75aa7289..750130a7b9dd 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -492,8 +492,8 @@ int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen); int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen); int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen); int security_locked_down(enum lockdown_reason what); -int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context, - size_t context_size, u64 id, u64 flags); +int lsm_fill_user_ctx(struct lsm_ctx __user *uctx, size_t *uctx_len, + void *val, size_t val_len, u64 id, u64 flags); #else /* CONFIG_SECURITY */ static inline int call_blocking_lsm_notifier(enum lsm_event event, void *data) @@ -1424,8 +1424,9 @@ static inline int security_locked_down(enum lockdown_reason what) { return 0; } -static inline int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context, - size_t context_size, u64 id, u64 flags) +static inline int lsm_fill_user_ctx(struct lsm_ctx __user *uctx, + size_t *uctx_len, void *val, size_t val_len, + u64 id, u64 flags) { return -EOPNOTSUPP; } diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c index 5e16c03936b9..6df97eb6e7d9 100644 --- a/security/apparmor/lsm.c +++ b/security/apparmor/lsm.c @@ -636,7 +636,6 @@ static int apparmor_getselfattr(unsigned int attr, struct lsm_ctx __user *lx, int error = -ENOENT; struct aa_task_ctx *ctx = task_ctx(current); struct aa_label *label = NULL; - size_t total_len = 0; char *value; switch (attr) { @@ -658,22 +657,14 @@ static int apparmor_getselfattr(unsigned int attr, struct lsm_ctx __user *lx, if (label) { error = aa_getprocattr(label, &value, false); - if (error > 0) { - total_len = ALIGN(struct_size(lx, ctx, error), 8); - if (total_len > *size) - error = -E2BIG; - else if (lx) - error = lsm_fill_user_ctx(lx, value, error, - LSM_ID_APPARMOR, 0); - else - error = 1; - } + if (error > 0) + error = lsm_fill_user_ctx(lx, size, value, error, + LSM_ID_APPARMOR, 0); kfree(value); } aa_put_label(label); - *size = total_len; if (error < 0) return error; return 1; diff --git a/security/security.c b/security/security.c index 67ded406a5ea..45c4f5440c95 100644 --- a/security/security.c +++ b/security/security.c @@ -773,42 +773,49 @@ static int lsm_superblock_alloc(struct super_block *sb) /** * lsm_fill_user_ctx - Fill a user space lsm_ctx structure - * @ctx: an LSM context to be filled - * @context: the new context value - * @context_size: the size of the new context value + * @uctx: a userspace LSM context to be filled + * @uctx_len: available uctx size (input), used uctx size (output) + * @val: the new LSM context value + * @val_len: the size of the new LSM context value * @id: LSM id * @flags: LSM defined flags * - * Fill all of the fields in a user space lsm_ctx structure. - * Caller is assumed to have verified that @ctx has enough space - * for @context. + * Fill all of the fields in a userspace lsm_ctx structure. * - * Returns 0 on success, -EFAULT on a copyout error, -ENOMEM - * if memory can't be allocated. + * Returns 0 on success, -E2BIG if userspace buffer is not large enough, + * -EFAULT on a copyout error, -ENOMEM if memory can't be allocated. */ -int lsm_fill_user_ctx(struct lsm_ctx __user *ctx, void *context, - size_t context_size, u64 id, u64 flags) +int lsm_fill_user_ctx(struct lsm_ctx __user *uctx, size_t *uctx_len, + void *val, size_t val_len, + u64 id, u64 flags) { - struct lsm_ctx *lctx; - size_t locallen = struct_size(lctx, ctx, context_size); + struct lsm_ctx *nctx = NULL; + size_t nctx_len; int rc = 0; - lctx = kzalloc(locallen, GFP_KERNEL); - if (lctx == NULL) - return -ENOMEM; + nctx_len = ALIGN(struct_size(nctx, ctx, val_len), BITS_PER_LONG / 8); + if (nctx_len > *uctx_len) { + rc = -E2BIG; + goto out; + } - lctx->id = id; - lctx->flags = flags; - lctx->ctx_len = context_size; - lctx->len = locallen; + nctx = kzalloc(nctx_len, GFP_KERNEL); + if (nctx == NULL) { + rc = -ENOMEM; + goto out; + } + nctx->id = id; + nctx->flags = flags; + nctx->len = nctx_len; + nctx->ctx_len = val_len; + memcpy(nctx->ctx, val, val_len); - memcpy(lctx->ctx, context, context_size); - - if (copy_to_user(ctx, lctx, locallen)) + if (copy_to_user(uctx, nctx, nctx_len)) rc = -EFAULT; - kfree(lctx); - +out: + kfree(nctx); + *uctx_len = nctx_len; return rc; } diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 1fe30e635923..c32794979aab 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -6480,30 +6480,32 @@ static int selinux_lsm_setattr(u64 attr, void *value, size_t size) return error; } +/** + * selinux_getselfattr - Get SELinux current task attributes + * @attr: the requested attribute + * @ctx: buffer to receive the result + * @size: buffer size (input), buffer size used (output) + * @flags: unused + * + * Fill the passed user space @ctx with the details of the requested + * attribute. + * + * Returns the number of attributes on success, an error code otherwise. + * There will only ever be one attribute. + */ static int selinux_getselfattr(unsigned int attr, struct lsm_ctx __user *ctx, size_t *size, u32 flags) { - char *value; - size_t total_len; - int len; - int rc = 0; + int rc; + char *val; + int val_len; - len = selinux_lsm_getattr(attr, current, &value); - if (len < 0) - return len; - - total_len = ALIGN(struct_size(ctx, ctx, len), 8); - - if (total_len > *size) - rc = -E2BIG; - else if (ctx) - rc = lsm_fill_user_ctx(ctx, value, len, LSM_ID_SELINUX, 0); - - kfree(value); - *size = total_len; - if (rc < 0) - return rc; - return 1; + val_len = selinux_lsm_getattr(attr, current, &val); + if (val_len < 0) + return val_len; + rc = lsm_fill_user_ctx(ctx, size, val, val_len, LSM_ID_SELINUX, 0); + kfree(val); + return (!rc ? 1 : rc); } static int selinux_setselfattr(unsigned int attr, struct lsm_ctx *ctx, diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index 12160d060cc1..99664c8cf867 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -3642,28 +3642,17 @@ static void smack_d_instantiate(struct dentry *opt_dentry, struct inode *inode) static int smack_getselfattr(unsigned int attr, struct lsm_ctx __user *ctx, size_t *size, u32 flags) { - struct smack_known *skp = smk_of_current(); - int total; - int slen; int rc; + struct smack_known *skp; if (attr != LSM_ATTR_CURRENT) return -EOPNOTSUPP; - slen = strlen(skp->smk_known) + 1; - total = ALIGN(slen + sizeof(*ctx), 8); - if (total > *size) - rc = -E2BIG; - else if (ctx) - rc = lsm_fill_user_ctx(ctx, skp->smk_known, slen, LSM_ID_SMACK, - 0); - else - rc = 1; - - *size = total; - if (rc >= 0) - return 1; - return rc; + skp = smk_of_current(); + rc = lsm_fill_user_ctx(ctx, size, + skp->smk_known, strlen(skp->smk_known) + 1, + LSM_ID_SMACK, 0); + return (!rc ? 1 : rc); } /**