linux-stable.git/kernel/bpf, branch v5.18.2 Linux kernel stable tree bpf: Do write access check for kfunc and global func 2022-06-06T06:49:00+00:00 Kumar Kartikeya Dwivedi memxor@gmail.com 2022-03-19T08:08:23+00:00 4caf12e7c81d96acfa268c8e44c721a8f036f52c commit be77354a3d7ebd4897ee18eca26dca6df9224c76 upstream. When passing pointer to some map value to kfunc or global func, in verifier we are passing meta as NULL to various functions, which uses meta->raw_mode to check whether memory is being written to. Since some kfunc or global funcs may also write to memory pointers they receive as arguments, we must check for write access to memory. E.g. in some case map may be read only and this will be missed by current checks. However meta->raw_mode allows for uninitialized memory (e.g. on stack), since there is not enough info available through BTF, we must perform one call for read access (raw_mode = false), and one for write access (raw_mode = true). Fixes: e5069b9c23b3 ("bpf: Support pointers in global func args") Fixes: d583691c47dc ("bpf: Introduce mem, size argument pair support for kfunc") Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20220319080827.73251-2-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit be77354a3d7ebd4897ee18eca26dca6df9224c76 upstream.

When passing pointer to some map value to kfunc or global func, in
verifier we are passing meta as NULL to various functions, which uses
meta->raw_mode to check whether memory is being written to. Since some
kfunc or global funcs may also write to memory pointers they receive as
arguments, we must check for write access to memory. E.g. in some case
map may be read only and this will be missed by current checks.

However meta->raw_mode allows for uninitialized memory (e.g. on stack),
since there is not enough info available through BTF, we must perform
one call for read access (raw_mode = false), and one for write access
(raw_mode = true).

Fixes: e5069b9c23b3 ("bpf: Support pointers in global func args")
Fixes: d583691c47dc ("bpf: Introduce mem, size argument pair support for kfunc")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20220319080827.73251-2-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
bpf: Check PTR_TO_MEM | MEM_RDONLY in check_helper_mem_access 2022-06-06T06:49:00+00:00 Kumar Kartikeya Dwivedi memxor@gmail.com 2022-03-19T08:08:24+00:00 717c39718dbc4f7ebcbb7b625fb11851cd9007fe commit 97e6d7dab1ca4648821c790a2b7913d6d5d549db upstream. The commit being fixed was aiming to disallow users from incorrectly obtaining writable pointer to memory that is only meant to be read. This is enforced now using a MEM_RDONLY flag. For instance, in case of global percpu variables, when the BTF type is not struct (e.g. bpf_prog_active), the verifier marks register type as PTR_TO_MEM | MEM_RDONLY from bpf_this_cpu_ptr or bpf_per_cpu_ptr helpers. However, when passing such pointer to kfunc, global funcs, or BPF helpers, in check_helper_mem_access, there is no expectation MEM_RDONLY flag will be set, hence it is checked as pointer to writable memory. Later, verifier sets up argument type of global func as PTR_TO_MEM | PTR_MAYBE_NULL, so user can use a global func to get around the limitations imposed by this flag. This check will also cover global non-percpu variables that may be introduced in kernel BTF in future. Also, we update the log message for PTR_TO_BUF case to be similar to PTR_TO_MEM case, so that the reason for error is clear to user. Fixes: 34d3a78c681e ("bpf: Make per_cpu_ptr return rdonly PTR_TO_MEM.") Reviewed-by: Hao Luo <haoluo@google.com> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20220319080827.73251-3-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 97e6d7dab1ca4648821c790a2b7913d6d5d549db upstream.

The commit being fixed was aiming to disallow users from incorrectly
obtaining writable pointer to memory that is only meant to be read. This
is enforced now using a MEM_RDONLY flag.

For instance, in case of global percpu variables, when the BTF type is
not struct (e.g. bpf_prog_active), the verifier marks register type as
PTR_TO_MEM | MEM_RDONLY from bpf_this_cpu_ptr or bpf_per_cpu_ptr
helpers. However, when passing such pointer to kfunc, global funcs, or
BPF helpers, in check_helper_mem_access, there is no expectation
MEM_RDONLY flag will be set, hence it is checked as pointer to writable
memory. Later, verifier sets up argument type of global func as
PTR_TO_MEM | PTR_MAYBE_NULL, so user can use a global func to get around
the limitations imposed by this flag.

This check will also cover global non-percpu variables that may be
introduced in kernel BTF in future.

Also, we update the log message for PTR_TO_BUF case to be similar to
PTR_TO_MEM case, so that the reason for error is clear to user.

Fixes: 34d3a78c681e ("bpf: Make per_cpu_ptr return rdonly PTR_TO_MEM.")
Reviewed-by: Hao Luo <haoluo@google.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20220319080827.73251-3-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
bpf: Reject writes for PTR_TO_MAP_KEY in check_helper_mem_access 2022-06-06T06:49:00+00:00 Kumar Kartikeya Dwivedi memxor@gmail.com 2022-03-19T08:08:25+00:00 a08d942ecbf46e23a192093f6983cb1d779f4fa8 commit 7b3552d3f9f6897851fc453b5131a967167e43c2 upstream. It is not permitted to write to PTR_TO_MAP_KEY, but the current code in check_helper_mem_access would allow for it, reject this case as well, as helpers taking ARG_PTR_TO_UNINIT_MEM also take PTR_TO_MAP_KEY. Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper") Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20220319080827.73251-4-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 7b3552d3f9f6897851fc453b5131a967167e43c2 upstream.

It is not permitted to write to PTR_TO_MAP_KEY, but the current code in
check_helper_mem_access would allow for it, reject this case as well, as
helpers taking ARG_PTR_TO_UNINIT_MEM also take PTR_TO_MAP_KEY.

Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper")
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20220319080827.73251-4-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
bpf: Fix excessive memory allocation in stack_map_alloc() 2022-06-06T06:48:59+00:00 Yuntao Wang ytcoode@gmail.com 2022-04-07T13:04:23+00:00 a31729c945fdcb9b3eea6fe14a1e94e7d39bd8c6 commit b45043192b3e481304062938a6561da2ceea46a6 upstream. The 'n_buckets * (value_size + sizeof(struct stack_map_bucket))' part of the allocated memory for 'smap' is never used after the memlock accounting was removed, thus get rid of it. [ Note, Daniel: Commit b936ca643ade ("bpf: rework memlock-based memory accounting for maps") moved `cost += n_buckets * (value_size + sizeof(struct stack_map_bucket))` up and therefore before the bpf_map_area_alloc() allocation, sigh. In a later step commit c85d69135a91 ("bpf: move memory size checks to bpf_map_charge_init()"), and the overflow checks of `cost >= U32_MAX - PAGE_SIZE` moved into bpf_map_charge_init(). And then 370868107bf6 ("bpf: Eliminate rlimit-based memory accounting for stackmap maps") finally removed the bpf_map_charge_init(). Anyway, the original code did the allocation same way as /after/ this fix. ] Fixes: b936ca643ade ("bpf: rework memlock-based memory accounting for maps") Signed-off-by: Yuntao Wang <ytcoode@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20220407130423.798386-1-ytcoode@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit b45043192b3e481304062938a6561da2ceea46a6 upstream.

The 'n_buckets * (value_size + sizeof(struct stack_map_bucket))' part of the
allocated memory for 'smap' is never used after the memlock accounting was
removed, thus get rid of it.

[ Note, Daniel:

Commit b936ca643ade ("bpf: rework memlock-based memory accounting for maps")
moved `cost += n_buckets * (value_size + sizeof(struct stack_map_bucket))`
up and therefore before the bpf_map_area_alloc() allocation, sigh. In a later
step commit c85d69135a91 ("bpf: move memory size checks to bpf_map_charge_init()"),
and the overflow checks of `cost >= U32_MAX - PAGE_SIZE` moved into
bpf_map_charge_init(). And then 370868107bf6 ("bpf: Eliminate rlimit-based
memory accounting for stackmap maps") finally removed the bpf_map_charge_init().
Anyway, the original code did the allocation same way as /after/ this fix. ]

Fixes: b936ca643ade ("bpf: rework memlock-based memory accounting for maps")
Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220407130423.798386-1-ytcoode@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
bpf: Fix usage of trace RCU in local storage. 2022-06-06T06:48:59+00:00 KP Singh kpsingh@kernel.org 2022-04-18T15:51:58+00:00 d2d2a1b6670bfac94a8b6a1fa9ce8b786cbe972e commit dcf456c9a095a6e71f53d6f6f004133ee851ee70 upstream. bpf_{sk,task,inode}_storage_free() do not need to use call_rcu_tasks_trace as no BPF program should be accessing the owner as it's being destroyed. The only other reader at this point is bpf_local_storage_map_free() which uses normal RCU. The only path that needs trace RCU are: * bpf_local_storage_{delete,update} helpers * map_{delete,update}_elem() syscalls Fixes: 0fe4b381a59e ("bpf: Allow bpf_local_storage to be used by sleepable programs") Signed-off-by: KP Singh <kpsingh@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Martin KaFai Lau <kafai@fb.com> Link: https://lore.kernel.org/bpf/20220418155158.2865678-1-kpsingh@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit dcf456c9a095a6e71f53d6f6f004133ee851ee70 upstream.

bpf_{sk,task,inode}_storage_free() do not need to use
call_rcu_tasks_trace as no BPF program should be accessing the owner
as it's being destroyed. The only other reader at this point is
bpf_local_storage_map_free() which uses normal RCU.

The only path that needs trace RCU are:

* bpf_local_storage_{delete,update} helpers
* map_{delete,update}_elem() syscalls

Fixes: 0fe4b381a59e ("bpf: Allow bpf_local_storage to be used by sleepable programs")
Signed-off-by: KP Singh <kpsingh@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20220418155158.2865678-1-kpsingh@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
bpf: Fix combination of jit blinding and pointers to bpf subprogs. 2022-06-06T06:48:59+00:00 Alexei Starovoitov ast@kernel.org 2022-05-13T01:10:24+00:00 d106a3e96fca30e44081eae9c27aab28fc132a46 commit 4b6313cf99b0d51b49aeaea98ec76ca8161ecb80 upstream. The combination of jit blinding and pointers to bpf subprogs causes: [ 36.989548] BUG: unable to handle page fault for address: 0000000100000001 [ 36.990342] #PF: supervisor instruction fetch in kernel mode [ 36.990968] #PF: error_code(0x0010) - not-present page [ 36.994859] RIP: 0010:0x100000001 [ 36.995209] Code: Unable to access opcode bytes at RIP 0xffffffd7. [ 37.004091] Call Trace: [ 37.004351] <TASK> [ 37.004576] ? bpf_loop+0x4d/0x70 [ 37.004932] ? bpf_prog_3899083f75e4c5de_F+0xe3/0x13b The jit blinding logic didn't recognize that ld_imm64 with an address of bpf subprogram is a special instruction and proceeded to randomize it. By itself it wouldn't have been an issue, but jit_subprogs() logic relies on two step process to JIT all subprogs and then JIT them again when addresses of all subprogs are known. Blinding process in the first JIT phase caused second JIT to miss adjustment of special ld_imm64. Fix this issue by ignoring special ld_imm64 instructions that don't have user controlled constants and shouldn't be blinded. Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper") Reported-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Martin KaFai Lau <kafai@fb.com> Link: https://lore.kernel.org/bpf/20220513011025.13344-1-alexei.starovoitov@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 4b6313cf99b0d51b49aeaea98ec76ca8161ecb80 upstream.

The combination of jit blinding and pointers to bpf subprogs causes:
[   36.989548] BUG: unable to handle page fault for address: 0000000100000001
[   36.990342] #PF: supervisor instruction fetch in kernel mode
[   36.990968] #PF: error_code(0x0010) - not-present page
[   36.994859] RIP: 0010:0x100000001
[   36.995209] Code: Unable to access opcode bytes at RIP 0xffffffd7.
[   37.004091] Call Trace:
[   37.004351]  <TASK>
[   37.004576]  ? bpf_loop+0x4d/0x70
[   37.004932]  ? bpf_prog_3899083f75e4c5de_F+0xe3/0x13b

The jit blinding logic didn't recognize that ld_imm64 with an address
of bpf subprogram is a special instruction and proceeded to randomize it.
By itself it wouldn't have been an issue, but jit_subprogs() logic
relies on two step process to JIT all subprogs and then JIT them
again when addresses of all subprogs are known.
Blinding process in the first JIT phase caused second JIT to miss
adjustment of special ld_imm64.

Fix this issue by ignoring special ld_imm64 instructions that don't have
user controlled constants and shouldn't be blinded.

Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper")
Reported-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20220513011025.13344-1-alexei.starovoitov@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
bpf: Fix potential array overflow in bpf_trampoline_get_progs() 2022-06-06T06:48:59+00:00 Yuntao Wang ytcoode@gmail.com 2022-04-30T13:08:03+00:00 4f8897bcc20b9ae44758e0572538d741ab66f0dc commit a2aa95b71c9bbec793b5c5fa50f0a80d882b3e8d upstream. The cnt value in the 'cnt >= BPF_MAX_TRAMP_PROGS' check does not include BPF_TRAMP_MODIFY_RETURN bpf programs, so the number of the attached BPF_TRAMP_MODIFY_RETURN bpf programs in a trampoline can exceed BPF_MAX_TRAMP_PROGS. When this happens, the assignment '*progs++ = aux->prog' in bpf_trampoline_get_progs() will cause progs array overflow as the progs field in the bpf_tramp_progs struct can only hold at most BPF_MAX_TRAMP_PROGS bpf programs. Fixes: 88fd9e5352fe ("bpf: Refactor trampoline update code") Signed-off-by: Yuntao Wang <ytcoode@gmail.com> Link: https://lore.kernel.org/r/20220430130803.210624-1-ytcoode@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit a2aa95b71c9bbec793b5c5fa50f0a80d882b3e8d upstream.

The cnt value in the 'cnt >= BPF_MAX_TRAMP_PROGS' check does not
include BPF_TRAMP_MODIFY_RETURN bpf programs, so the number of
the attached BPF_TRAMP_MODIFY_RETURN bpf programs in a trampoline
can exceed BPF_MAX_TRAMP_PROGS.

When this happens, the assignment '*progs++ = aux->prog' in
bpf_trampoline_get_progs() will cause progs array overflow as the
progs field in the bpf_tramp_progs struct can only hold at most
BPF_MAX_TRAMP_PROGS bpf programs.

Fixes: 88fd9e5352fe ("bpf: Refactor trampoline update code")
Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
Link: https://lore.kernel.org/r/20220430130803.210624-1-ytcoode@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
bpf: Fill new bpf_prog_pack with illegal instructions 2022-06-06T06:48:59+00:00 Song Liu song@kernel.org 2022-05-20T23:57:51+00:00 8da0d2d056beaff23e12e543f6828f7c61e02d52 commit d88bb5eed04ce50cc20e7f9282977841728be798 upstream. bpf_prog_pack enables sharing huge pages among multiple BPF programs. These pages are marked as executable before the JIT engine fill it with BPF programs. To make these pages safe, fill the hole bpf_prog_pack with illegal instructions before making it executable. Fixes: 57631054fae6 ("bpf: Introduce bpf_prog_pack allocator") Fixes: 33c9805860e5 ("bpf: Introduce bpf_jit_binary_pack_[alloc|finalize|free]") Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Song Liu <song@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20220520235758.1858153-2-song@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit d88bb5eed04ce50cc20e7f9282977841728be798 upstream.

bpf_prog_pack enables sharing huge pages among multiple BPF programs.
These pages are marked as executable before the JIT engine fill it with
BPF programs. To make these pages safe, fill the hole bpf_prog_pack with
illegal instructions before making it executable.

Fixes: 57631054fae6 ("bpf: Introduce bpf_prog_pack allocator")
Fixes: 33c9805860e5 ("bpf: Introduce bpf_jit_binary_pack_[alloc|finalize|free]")
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220520235758.1858153-2-song@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
bpf: Fix maximum permitted number of arguments check 2022-03-29T02:08:17+00:00 Yuntao Wang ytcoode@gmail.com 2022-03-24T16:42:38+00:00 c29a4920dfcaa1433b09e2674f605f72767a385c Since the m->arg_size array can hold up to MAX_BPF_FUNC_ARGS argument sizes, it's ok that nargs is equal to MAX_BPF_FUNC_ARGS. Signed-off-by: Yuntao Wang <ytcoode@gmail.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Martin KaFai Lau <kafai@fb.com> Link: https://lore.kernel.org/bpf/20220324164238.1274915-1-ytcoode@gmail.com 
Since the m->arg_size array can hold up to MAX_BPF_FUNC_ARGS argument
sizes, it's ok that nargs is equal to MAX_BPF_FUNC_ARGS.

Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20220324164238.1274915-1-ytcoode@gmail.com
Merge tag 'x86_core_for_5.18_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2022-03-27T17:17:23+00:00 Linus Torvalds torvalds@linux-foundation.org 2022-03-27T17:17:23+00:00 7001052160d172f6de06adeffde24dde9935ece8 Pull x86 CET-IBT (Control-Flow-Integrity) support from Peter Zijlstra: "Add support for Intel CET-IBT, available since Tigerlake (11th gen), which is a coarse grained, hardware based, forward edge Control-Flow-Integrity mechanism where any indirect CALL/JMP must target an ENDBR instruction or suffer #CP. Additionally, since Alderlake (12th gen)/Sapphire-Rapids, speculation is limited to 2 instructions (and typically fewer) on branch targets not starting with ENDBR. CET-IBT also limits speculation of the next sequential instruction after the indirect CALL/JMP [1]. CET-IBT is fundamentally incompatible with retpolines, but provides, as described above, speculation limits itself" [1] https://www.intel.com/content/www/us/en/developer/articles/technical/software-security-guidance/technical-documentation/branch-history-injection.html * tag 'x86_core_for_5.18_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (53 commits) kvm/emulate: Fix SETcc emulation for ENDBR x86/Kconfig: Only allow CONFIG_X86_KERNEL_IBT with ld.lld >= 14.0.0 x86/Kconfig: Only enable CONFIG_CC_HAS_IBT for clang >= 14.0.0 kbuild: Fixup the IBT kbuild changes x86/Kconfig: Do not allow CONFIG_X86_X32_ABI=y with llvm-objcopy x86: Remove toolchain check for X32 ABI capability x86/alternative: Use .ibt_endbr_seal to seal indirect calls objtool: Find unused ENDBR instructions objtool: Validate IBT assumptions objtool: Add IBT/ENDBR decoding objtool: Read the NOENDBR annotation x86: Annotate idtentry_df() x86,objtool: Move the ASM_REACHABLE annotation to objtool.h x86: Annotate call_on_stack() objtool: Rework ASM_REACHABLE x86: Mark __invalid_creds() __noreturn exit: Mark do_group_exit() __noreturn x86: Mark stop_this_cpu() __noreturn objtool: Ignore extra-symbol code objtool: Rename --duplicate to --lto ... 
Pull x86 CET-IBT (Control-Flow-Integrity) support from Peter Zijlstra:
 "Add support for Intel CET-IBT, available since Tigerlake (11th gen),
  which is a coarse grained, hardware based, forward edge
  Control-Flow-Integrity mechanism where any indirect CALL/JMP must
  target an ENDBR instruction or suffer #CP.

  Additionally, since Alderlake (12th gen)/Sapphire-Rapids, speculation
  is limited to 2 instructions (and typically fewer) on branch targets
  not starting with ENDBR. CET-IBT also limits speculation of the next
  sequential instruction after the indirect CALL/JMP [1].

  CET-IBT is fundamentally incompatible with retpolines, but provides,
  as described above, speculation limits itself"

[1] https://www.intel.com/content/www/us/en/developer/articles/technical/software-security-guidance/technical-documentation/branch-history-injection.html

* tag 'x86_core_for_5.18_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (53 commits)
  kvm/emulate: Fix SETcc emulation for ENDBR
  x86/Kconfig: Only allow CONFIG_X86_KERNEL_IBT with ld.lld >= 14.0.0
  x86/Kconfig: Only enable CONFIG_CC_HAS_IBT for clang >= 14.0.0
  kbuild: Fixup the IBT kbuild changes
  x86/Kconfig: Do not allow CONFIG_X86_X32_ABI=y with llvm-objcopy
  x86: Remove toolchain check for X32 ABI capability
  x86/alternative: Use .ibt_endbr_seal to seal indirect calls
  objtool: Find unused ENDBR instructions
  objtool: Validate IBT assumptions
  objtool: Add IBT/ENDBR decoding
  objtool: Read the NOENDBR annotation
  x86: Annotate idtentry_df()
  x86,objtool: Move the ASM_REACHABLE annotation to objtool.h
  x86: Annotate call_on_stack()
  objtool: Rework ASM_REACHABLE
  x86: Mark __invalid_creds() __noreturn
  exit: Mark do_group_exit() __noreturn
  x86: Mark stop_this_cpu() __noreturn
  objtool: Ignore extra-symbol code
  objtool: Rename --duplicate to --lto
  ...