From 2aff9d20d50ac45dd13a013ef5231f4fb8912356 Mon Sep 17 00:00:00 2001 From: Casey Schaufler Date: Wed, 10 Jul 2024 14:32:25 -0700 Subject: lsm: infrastructure management of the sock security Move management of the sock->sk_security blob out of the individual security modules and into the security infrastructure. Instead of allocating the blobs from within the modules the modules tell the infrastructure how much space is required, and the space is allocated there. Acked-by: Paul Moore Reviewed-by: Kees Cook Reviewed-by: John Johansen Acked-by: Stephen Smalley Signed-off-by: Casey Schaufler [PM: subject tweak] Signed-off-by: Paul Moore --- include/linux/lsm_hooks.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/lsm_hooks.h') diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index a2ade0ffe9e7..efd4a0655159 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -73,6 +73,7 @@ struct lsm_blob_sizes { int lbs_cred; int lbs_file; int lbs_inode; + int lbs_sock; int lbs_superblock; int lbs_ipc; int lbs_msg_msg; -- cgit v1.2.3 From 5f8d28f6d7d568dbbc8c5bce94894474c07afd4f Mon Sep 17 00:00:00 2001 From: Casey Schaufler Date: Wed, 10 Jul 2024 14:32:26 -0700 Subject: lsm: infrastructure management of the key security blob Move management of the key->security blob out of the individual security modules and into the security infrastructure. Instead of allocating the blobs from within the modules the modules tell the infrastructure how much space is required, and the space is allocated there. There are no existing modules that require a key_free hook, so the call to it and the definition for it have been removed. Signed-off-by: Casey Schaufler Reviewed-by: John Johansen [PM: subject tweak] Signed-off-by: Paul Moore --- include/linux/lsm_hooks.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/lsm_hooks.h') diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index efd4a0655159..7233bc0737be 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -76,6 +76,7 @@ struct lsm_blob_sizes { int lbs_sock; int lbs_superblock; int lbs_ipc; + int lbs_key; int lbs_msg_msg; int lbs_task; int lbs_xattr_count; /* number of xattr slots in new_xattrs array */ -- cgit v1.2.3 From a39c0f77dbbe083f3eec6c3b32d90f168f7575eb Mon Sep 17 00:00:00 2001 From: Casey Schaufler Date: Wed, 10 Jul 2024 14:32:28 -0700 Subject: lsm: infrastructure management of the dev_tun blob Move management of the dev_tun security blob out of the individual security modules and into the LSM infrastructure. The security modules tell the infrastructure how much space they require at initialization. There are no longer any modules that require the dev_tun_free hook. The hook definition has been removed. Signed-off-by: Casey Schaufler Reviewed-by: John Johansen [PM: subject tweak, selinux style fixes] Signed-off-by: Paul Moore --- include/linux/lsm_hooks.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/lsm_hooks.h') diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 7233bc0737be..0ff14ff128c8 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -80,6 +80,7 @@ struct lsm_blob_sizes { int lbs_msg_msg; int lbs_task; int lbs_xattr_count; /* number of xattr slots in new_xattrs array */ + int lbs_tun_dev; }; /** -- cgit v1.2.3 From 66de33a0bbb59ef3909d2c65dbbb7fc503d573bd Mon Sep 17 00:00:00 2001 From: Casey Schaufler Date: Wed, 10 Jul 2024 14:32:29 -0700 Subject: lsm: infrastructure management of the infiniband blob Move management of the infiniband security blob out of the individual security modules and into the LSM infrastructure. The security modules tell the infrastructure how much space they require at initialization. There are no longer any modules that require the ib_free() hook. The hook definition has been removed. Signed-off-by: Casey Schaufler Reviewed-by: John Johansen [PM: subject tweak, selinux style fixes] Signed-off-by: Paul Moore --- include/linux/lsm_hooks.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/lsm_hooks.h') diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 0ff14ff128c8..b6fc6ac88723 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -72,6 +72,7 @@ struct security_hook_list { struct lsm_blob_sizes { int lbs_cred; int lbs_file; + int lbs_ib; int lbs_inode; int lbs_sock; int lbs_superblock; -- cgit v1.2.3 From 61a1dcdceb44d79e5ab511295791b88ea178c045 Mon Sep 17 00:00:00 2001 From: Casey Schaufler Date: Wed, 10 Jul 2024 14:32:30 -0700 Subject: lsm: infrastructure management of the perf_event security blob Move management of the perf_event->security blob out of the individual security modules and into the security infrastructure. Instead of allocating the blobs from within the modules the modules tell the infrastructure how much space is required, and the space is allocated there. There are no longer any modules that require the perf_event_free() hook. The hook definition has been removed. Signed-off-by: Casey Schaufler Reviewed-by: John Johansen [PM: subject tweak] Signed-off-by: Paul Moore --- include/linux/lsm_hooks.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/lsm_hooks.h') diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index b6fc6ac88723..f1ca8082075a 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -79,6 +79,7 @@ struct lsm_blob_sizes { int lbs_ipc; int lbs_key; int lbs_msg_msg; + int lbs_perf_event; int lbs_task; int lbs_xattr_count; /* number of xattr slots in new_xattrs array */ int lbs_tun_dev; -- cgit v1.2.3 From 711f5c5ce6c2c640c1b3b569ab2a8847be5ab21f Mon Sep 17 00:00:00 2001 From: Paul Moore Date: Mon, 15 Jul 2024 21:22:51 -0400 Subject: lsm: cleanup lsm_hooks.h Some cleanup and style corrections for lsm_hooks.h. * Drop the lsm_inode_alloc() extern declaration, it is not needed. * Relocate lsm_get_xattr_slot() and extern variables in the file to improve grouping of related objects. * Don't use tabs to needlessly align structure fields. Reviewed-by: Casey Schaufler Signed-off-by: Paul Moore --- include/linux/lsm_hooks.h | 87 +++++++++++++++++++++++------------------------ 1 file changed, 43 insertions(+), 44 deletions(-) (limited to 'include/linux/lsm_hooks.h') diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index f1ca8082075a..11ea0063228f 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -51,8 +51,8 @@ struct security_hook_heads { * Contains the information that identifies the LSM. */ struct lsm_id { - const char *name; - u64 id; + const char *name; + u64 id; }; /* @@ -60,49 +60,31 @@ struct lsm_id { * For use with generic list macros for common operations. */ struct security_hook_list { - struct hlist_node list; - struct hlist_head *head; - union security_list_options hook; - const struct lsm_id *lsmid; + struct hlist_node list; + struct hlist_head *head; + union security_list_options hook; + const struct lsm_id *lsmid; } __randomize_layout; /* * Security blob size or offset data. */ struct lsm_blob_sizes { - int lbs_cred; - int lbs_file; - int lbs_ib; - int lbs_inode; - int lbs_sock; - int lbs_superblock; - int lbs_ipc; - int lbs_key; - int lbs_msg_msg; - int lbs_perf_event; - int lbs_task; - int lbs_xattr_count; /* number of xattr slots in new_xattrs array */ - int lbs_tun_dev; + int lbs_cred; + int lbs_file; + int lbs_ib; + int lbs_inode; + int lbs_sock; + int lbs_superblock; + int lbs_ipc; + int lbs_key; + int lbs_msg_msg; + int lbs_perf_event; + int lbs_task; + int lbs_xattr_count; /* number of xattr slots in new_xattrs array */ + int lbs_tun_dev; }; -/** - * lsm_get_xattr_slot - Return the next available slot and increment the index - * @xattrs: array storing LSM-provided xattrs - * @xattr_count: number of already stored xattrs (updated) - * - * Retrieve the first available slot in the @xattrs array to fill with an xattr, - * and increment @xattr_count. - * - * Return: The slot to fill in @xattrs if non-NULL, NULL otherwise. - */ -static inline struct xattr *lsm_get_xattr_slot(struct xattr *xattrs, - int *xattr_count) -{ - if (unlikely(!xattrs)) - return NULL; - return &xattrs[(*xattr_count)++]; -} - /* * LSM_RET_VOID is used as the default value in LSM_HOOK definitions for void * LSM hooks (in include/linux/lsm_hook_defs.h). @@ -118,9 +100,6 @@ static inline struct xattr *lsm_get_xattr_slot(struct xattr *xattrs, #define LSM_HOOK_INIT(HEAD, HOOK) \ { .head = &security_hook_heads.HEAD, .hook = { .HEAD = HOOK } } -extern struct security_hook_heads security_hook_heads; -extern char *lsm_names; - extern void security_add_hooks(struct security_hook_list *hooks, int count, const struct lsm_id *lsmid); @@ -142,9 +121,6 @@ struct lsm_info { struct lsm_blob_sizes *blobs; /* Optional: for blob sharing. */ }; -extern struct lsm_info __start_lsm_info[], __end_lsm_info[]; -extern struct lsm_info __start_early_lsm_info[], __end_early_lsm_info[]; - #define DEFINE_LSM(lsm) \ static struct lsm_info __lsm_##lsm \ __used __section(".lsm_info.init") \ @@ -155,6 +131,29 @@ extern struct lsm_info __start_early_lsm_info[], __end_early_lsm_info[]; __used __section(".early_lsm_info.init") \ __aligned(sizeof(unsigned long)) -extern int lsm_inode_alloc(struct inode *inode); +/* DO NOT tamper with these variables outside of the LSM framework */ +extern char *lsm_names; +extern struct security_hook_heads security_hook_heads; +extern struct lsm_static_calls_table static_calls_table __ro_after_init; +extern struct lsm_info __start_lsm_info[], __end_lsm_info[]; +extern struct lsm_info __start_early_lsm_info[], __end_early_lsm_info[]; + +/** + * lsm_get_xattr_slot - Return the next available slot and increment the index + * @xattrs: array storing LSM-provided xattrs + * @xattr_count: number of already stored xattrs (updated) + * + * Retrieve the first available slot in the @xattrs array to fill with an xattr, + * and increment @xattr_count. + * + * Return: The slot to fill in @xattrs if non-NULL, NULL otherwise. + */ +static inline struct xattr *lsm_get_xattr_slot(struct xattr *xattrs, + int *xattr_count) +{ + if (unlikely(!xattrs)) + return NULL; + return &xattrs[(*xattr_count)++]; +} #endif /* ! __LINUX_LSM_HOOKS_H */ -- cgit v1.2.3 From b55d26bd1891423a3cdccf816b386aec8bbefc87 Mon Sep 17 00:00:00 2001 From: Deven Bowers Date: Fri, 2 Aug 2024 23:08:25 -0700 Subject: block,lsm: add LSM blob and new LSM hooks for block devices This patch introduces a new LSM blob to the block_device structure, enabling the security subsystem to store security-sensitive data related to block devices. Currently, for a device mapper's mapped device containing a dm-verity target, critical security information such as the roothash and its signing state are not readily accessible. Specifically, while the dm-verity volume creation process passes the dm-verity roothash and its signature from userspace to the kernel, the roothash is stored privately within the dm-verity target, and its signature is discarded post-verification. This makes it extremely hard for the security subsystem to utilize these data. With the addition of the LSM blob to the block_device structure, the security subsystem can now retain and manage important security metadata such as the roothash and the signing state of a dm-verity by storing them inside the blob. Access decisions can then be based on these stored data. The implementation follows the same approach used for security blobs in other structures like struct file, struct inode, and struct superblock. The initialization of the security blob occurs after the creation of the struct block_device, performed by the security subsystem. Similarly, the security blob is freed by the security subsystem before the struct block_device is deallocated or freed. This patch also introduces a new hook security_bdev_setintegrity() to save block device's integrity data to the new LSM blob. For example, for dm-verity, it can use this hook to expose its roothash and signing state to LSMs, then LSMs can save these data into the LSM blob. Please note that the new hook should be invoked every time the security information is updated to keep these data current. For example, in dm-verity, if the mapping table is reloaded and configured to use a different dm-verity target with a new roothash and signing information, the previously stored data in the LSM blob will become obsolete. It is crucial to re-invoke the hook to refresh these data and ensure they are up to date. This necessity arises from the design of device-mapper, where a device-mapper device is first created, and then targets are subsequently loaded into it. These targets can be modified multiple times during the device's lifetime. Therefore, while the LSM blob is allocated during the creation of the block device, its actual contents are not initialized at this stage and can change substantially over time. This includes alterations from data that the LSM 'trusts' to those it does not, making it essential to handle these changes correctly. Failure to address this dynamic aspect could potentially allow for bypassing LSM checks. Signed-off-by: Deven Bowers Signed-off-by: Fan Wu [PM: merge fuzz, subject line tweaks] Signed-off-by: Paul Moore --- include/linux/lsm_hooks.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/lsm_hooks.h') diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 11ea0063228f..4687985b9175 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -83,6 +83,7 @@ struct lsm_blob_sizes { int lbs_task; int lbs_xattr_count; /* number of xattr slots in new_xattrs array */ int lbs_tun_dev; + int lbs_bdev; }; /* -- cgit v1.2.3 From 417c5643cd67a55f424b203b492082035d0236c3 Mon Sep 17 00:00:00 2001 From: KP Singh Date: Fri, 16 Aug 2024 17:43:07 +0200 Subject: lsm: replace indirect LSM hook calls with static calls LSM hooks are currently invoked from a linked list as indirect calls which are invoked using retpolines as a mitigation for speculative attacks (Branch History / Target injection) and add extra overhead which is especially bad in kernel hot paths: security_file_ioctl: 0xff...0320 <+0>: endbr64 0xff...0324 <+4>: push %rbp 0xff...0325 <+5>: push %r15 0xff...0327 <+7>: push %r14 0xff...0329 <+9>: push %rbx 0xff...032a <+10>: mov %rdx,%rbx 0xff...032d <+13>: mov %esi,%ebp 0xff...032f <+15>: mov %rdi,%r14 0xff...0332 <+18>: mov $0xff...7030,%r15 0xff...0339 <+25>: mov (%r15),%r15 0xff...033c <+28>: test %r15,%r15 0xff...033f <+31>: je 0xff...0358 0xff...0341 <+33>: mov 0x18(%r15),%r11 0xff...0345 <+37>: mov %r14,%rdi 0xff...0348 <+40>: mov %ebp,%esi 0xff...034a <+42>: mov %rbx,%rdx 0xff...034d <+45>: call 0xff...2e0 <__x86_indirect_thunk_array+352> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Indirect calls that use retpolines leading to overhead, not just due to extra instruction but also branch misses. 0xff...0352 <+50>: test %eax,%eax 0xff...0354 <+52>: je 0xff...0339 0xff...0356 <+54>: jmp 0xff...035a 0xff...0358 <+56>: xor %eax,%eax 0xff...035a <+58>: pop %rbx 0xff...035b <+59>: pop %r14 0xff...035d <+61>: pop %r15 0xff...035f <+63>: pop %rbp 0xff...0360 <+64>: jmp 0xff...47c4 <__x86_return_thunk> The indirect calls are not really needed as one knows the addresses of enabled LSM callbacks at boot time and only the order can possibly change at boot time with the lsm= kernel command line parameter. An array of static calls is defined per LSM hook and the static calls are updated at boot time once the order has been determined. With the hook now exposed as a static call, one can see that the retpolines are no longer there and the LSM callbacks are invoked directly: security_file_ioctl: 0xff...0ca0 <+0>: endbr64 0xff...0ca4 <+4>: nopl 0x0(%rax,%rax,1) 0xff...0ca9 <+9>: push %rbp 0xff...0caa <+10>: push %r14 0xff...0cac <+12>: push %rbx 0xff...0cad <+13>: mov %rdx,%rbx 0xff...0cb0 <+16>: mov %esi,%ebp 0xff...0cb2 <+18>: mov %rdi,%r14 0xff...0cb5 <+21>: jmp 0xff...0cc7 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Static key enabled for SELinux 0xffffffff818f0cb7 <+23>: jmp 0xff...0cde ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Static key enabled for BPF LSM. This is something that is changed to default to false to avoid the existing side effect issues of BPF LSM [1] in a subsequent patch. 0xff...0cb9 <+25>: xor %eax,%eax 0xff...0cbb <+27>: xchg %ax,%ax 0xff...0cbd <+29>: pop %rbx 0xff...0cbe <+30>: pop %r14 0xff...0cc0 <+32>: pop %rbp 0xff...0cc1 <+33>: cs jmp 0xff...0000 <__x86_return_thunk> 0xff...0cc7 <+39>: endbr64 0xff...0ccb <+43>: mov %r14,%rdi 0xff...0cce <+46>: mov %ebp,%esi 0xff...0cd0 <+48>: mov %rbx,%rdx 0xff...0cd3 <+51>: call 0xff...3230 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Direct call to SELinux. 0xff...0cd8 <+56>: test %eax,%eax 0xff...0cda <+58>: jne 0xff...0cbd 0xff...0cdc <+60>: jmp 0xff...0cb7 0xff...0cde <+62>: endbr64 0xff...0ce2 <+66>: mov %r14,%rdi 0xff...0ce5 <+69>: mov %ebp,%esi 0xff...0ce7 <+71>: mov %rbx,%rdx 0xff...0cea <+74>: call 0xff...e220 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Direct call to BPF LSM. 0xff...0cef <+79>: test %eax,%eax 0xff...0cf1 <+81>: jne 0xff...0cbd 0xff...0cf3 <+83>: jmp 0xff...0cb9 0xff...0cf5 <+85>: endbr64 0xff...0cf9 <+89>: mov %r14,%rdi 0xff...0cfc <+92>: mov %ebp,%esi 0xff...0cfe <+94>: mov %rbx,%rdx 0xff...0d01 <+97>: pop %rbx 0xff...0d02 <+98>: pop %r14 0xff...0d04 <+100>: pop %rbp 0xff...0d05 <+101>: ret 0xff...0d06 <+102>: int3 0xff...0d07 <+103>: int3 0xff...0d08 <+104>: int3 0xff...0d09 <+105>: int3 While this patch uses static_branch_unlikely indicating that an LSM hook is likely to be not present. In most cases this is still a better choice as even when an LSM with one hook is added, empty slots are created for all LSM hooks (especially when many LSMs that do not initialize most hooks are present on the system). There are some hooks that don't use the call_int_hook or call_void_hook. These hooks are updated to use a new macro called lsm_for_each_hook where the lsm_callback is directly invoked as an indirect call. Below are results of the relevant Unixbench system benchmarks with BPF LSM and SELinux enabled with default policies enabled with and without these patches. Benchmark Delta(%): (+ is better) ========================================================================== Execl Throughput +1.9356 File Write 1024 bufsize 2000 maxblocks +6.5953 Pipe Throughput +9.5499 Pipe-based Context Switching +3.0209 Process Creation +2.3246 Shell Scripts (1 concurrent) +1.4975 System Call Overhead +2.7815 System Benchmarks Index Score (Partial Only): +3.4859 In the best case, some syscalls like eventfd_create benefitted to about ~10%. Tested-by: Guenter Roeck Reviewed-by: Casey Schaufler Reviewed-by: Kees Cook Acked-by: Song Liu Acked-by: Andrii Nakryiko Signed-off-by: KP Singh Signed-off-by: Paul Moore --- include/linux/lsm_hooks.h | 52 +++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 43 insertions(+), 9 deletions(-) (limited to 'include/linux/lsm_hooks.h') diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 4687985b9175..090d1d3e19fe 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -30,19 +30,47 @@ #include #include #include +#include +#include +#include +#include union security_list_options { #define LSM_HOOK(RET, DEFAULT, NAME, ...) RET (*NAME)(__VA_ARGS__); #include "lsm_hook_defs.h" #undef LSM_HOOK + void *lsm_func_addr; }; -struct security_hook_heads { - #define LSM_HOOK(RET, DEFAULT, NAME, ...) struct hlist_head NAME; - #include "lsm_hook_defs.h" - #undef LSM_HOOK +/* + * @key: static call key as defined by STATIC_CALL_KEY + * @trampoline: static call trampoline as defined by STATIC_CALL_TRAMP + * @hl: The security_hook_list as initialized by the owning LSM. + * @active: Enabled when the static call has an LSM hook associated. + */ +struct lsm_static_call { + struct static_call_key *key; + void *trampoline; + struct security_hook_list *hl; + /* this needs to be true or false based on what the key defaults to */ + struct static_key_false *active; } __randomize_layout; +/* + * Table of the static calls for each LSM hook. + * Once the LSMs are initialized, their callbacks will be copied to these + * tables such that the calls are filled backwards (from last to first). + * This way, we can jump directly to the first used static call, and execute + * all of them after. This essentially makes the entry point + * dynamic to adapt the number of static calls to the number of callbacks. + */ +struct lsm_static_calls_table { + #define LSM_HOOK(RET, DEFAULT, NAME, ...) \ + struct lsm_static_call NAME[MAX_LSM_COUNT]; + #include + #undef LSM_HOOK +} __packed __randomize_layout; + /** * struct lsm_id - Identify a Linux Security Module. * @lsm: name of the LSM, must be approved by the LSM maintainers @@ -58,10 +86,14 @@ struct lsm_id { /* * Security module hook list structure. * For use with generic list macros for common operations. + * + * struct security_hook_list - Contents of a cacheable, mappable object. + * @scalls: The beginning of the array of static calls assigned to this hook. + * @hook: The callback for the hook. + * @lsm: The name of the lsm that owns this hook. */ struct security_hook_list { - struct hlist_node list; - struct hlist_head *head; + struct lsm_static_call *scalls; union security_list_options hook; const struct lsm_id *lsmid; } __randomize_layout; @@ -98,8 +130,11 @@ struct lsm_blob_sizes { * care of the common case and reduces the amount of * text involved. */ -#define LSM_HOOK_INIT(HEAD, HOOK) \ - { .head = &security_hook_heads.HEAD, .hook = { .HEAD = HOOK } } +#define LSM_HOOK_INIT(NAME, HOOK) \ + { \ + .scalls = static_calls_table.NAME, \ + .hook = { .NAME = HOOK } \ + } extern void security_add_hooks(struct security_hook_list *hooks, int count, const struct lsm_id *lsmid); @@ -134,7 +169,6 @@ struct lsm_info { /* DO NOT tamper with these variables outside of the LSM framework */ extern char *lsm_names; -extern struct security_hook_heads security_hook_heads; extern struct lsm_static_calls_table static_calls_table __ro_after_init; extern struct lsm_info __start_lsm_info[], __end_lsm_info[]; extern struct lsm_info __start_early_lsm_info[], __end_early_lsm_info[]; -- cgit v1.2.3