From: Thadeu Lima de Souza Cascardo cascardo@canonical.com
This reverts commit 00b136bb6254e0abf6aaafe62c4da5f6c4fea4cb.
This temporarily reverts the backport of upstream commit 1f001e9da6bbf482311e45e48f53c2bd2179e59c. It was not correct to copy the ftrace stub as it would contain a relative jump to the return thunk which would not apply to the context where it was being copied to, leading to ftrace support to be broken.
Signed-off-by: Thadeu Lima de Souza Cascardo cascardo@canonical.com Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com --- This series fixes the CONFIG_KPROBES_SANITY_TEST=y boot panic reported here: https://lore.kernel.org/stable/20220805200438.GC42579@windriver.com/
The fixes were backported from v5.15.62. Minor contextual adjustments were made in arch/x86/kernel/ftrace_64.S for the backport of e52fc2cf3f66 ("x86/ibt,ftrace: Make function-graph play nice").
arch/x86/kernel/ftrace.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 9a8633a6506c..449e31a2f124 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -309,7 +309,7 @@ union ftrace_op_code_union { } __attribute__((packed)); };
-#define RET_SIZE (IS_ENABLED(CONFIG_RETPOLINE) ? 5 : 1 + IS_ENABLED(CONFIG_SLS)) +#define RET_SIZE 1 + IS_ENABLED(CONFIG_SLS)
static unsigned long create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) @@ -368,10 +368,7 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
/* The trampoline ends with ret(q) */ retq = (unsigned long)ftrace_stub; - if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) - memcpy(ip, text_gen_insn(JMP32_INSN_OPCODE, ip, &__x86_return_thunk), JMP32_INSN_SIZE); - else - ret = copy_from_kernel_nofault(ip, (void *)retq, RET_SIZE); + ret = copy_from_kernel_nofault(ip, (void *)retq, RET_SIZE); if (WARN_ON(ret < 0)) goto fail;
From: Peter Zijlstra peterz@infradead.org
commit e52fc2cf3f662828cc0d51c4b73bed73ad275fce upstream.
Return trampoline must not use indirect branch to return; while this preserves the RSB, it is fundamentally incompatible with IBT. Instead use a retpoline like ROP gadget that defeats IBT while not unbalancing the RSB.
And since ftrace_stub is no longer a plain RET, don't use it to copy from. Since RET is a trivial instruction, poke it directly.
Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: Josh Poimboeuf jpoimboe@redhat.com Link: https://lore.kernel.org/r/20220308154318.347296408@infradead.org [cascardo: remove ENDBR] Signed-off-by: Thadeu Lima de Souza Cascardo cascardo@canonical.com [OP: adjusted context for 5.10-stable] Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com --- arch/x86/kernel/ftrace.c | 9 ++------- arch/x86/kernel/ftrace_64.S | 19 +++++++++++++++---- 2 files changed, 17 insertions(+), 11 deletions(-)
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 449e31a2f124..b80e38cbd49e 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -322,12 +322,12 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) unsigned long offset; unsigned long npages; unsigned long size; - unsigned long retq; unsigned long *ptr; void *trampoline; void *ip; /* 48 8b 15 <offset> is movq <offset>(%rip), %rdx */ unsigned const char op_ref[] = { 0x48, 0x8b, 0x15 }; + unsigned const char retq[] = { RET_INSN_OPCODE, INT3_INSN_OPCODE }; union ftrace_op_code_union op_ptr; int ret;
@@ -365,12 +365,7 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) goto fail;
ip = trampoline + size; - - /* The trampoline ends with ret(q) */ - retq = (unsigned long)ftrace_stub; - ret = copy_from_kernel_nofault(ip, (void *)retq, RET_SIZE); - if (WARN_ON(ret < 0)) - goto fail; + memcpy(ip, retq, RET_SIZE);
/* No need to test direct calls on created trampolines */ if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) { diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S index e3a375185a1b..5b2dabedcf66 100644 --- a/arch/x86/kernel/ftrace_64.S +++ b/arch/x86/kernel/ftrace_64.S @@ -170,7 +170,6 @@ SYM_INNER_LABEL(ftrace_graph_call, SYM_L_GLOBAL)
/* * This is weak to keep gas from relaxing the jumps. - * It is also used to copy the RET for trampolines. */ SYM_INNER_LABEL_ALIGN(ftrace_stub, SYM_L_WEAK) UNWIND_HINT_FUNC @@ -325,7 +324,7 @@ SYM_FUNC_END(ftrace_graph_caller)
SYM_CODE_START(return_to_handler) UNWIND_HINT_EMPTY - subq $24, %rsp + subq $16, %rsp
/* Save the return values */ movq %rax, (%rsp) @@ -337,7 +336,19 @@ SYM_CODE_START(return_to_handler) movq %rax, %rdi movq 8(%rsp), %rdx movq (%rsp), %rax - addq $24, %rsp - JMP_NOSPEC rdi + + addq $16, %rsp + /* + * Jump back to the old return address. This cannot be JMP_NOSPEC rdi + * since IBT would demand that contain ENDBR, which simply isn't so for + * return addresses. Use a retpoline here to keep the RSB balanced. + */ + ANNOTATE_INTRA_FUNCTION_CALL + call .Ldo_rop + int3 +.Ldo_rop: + mov %rdi, (%rsp) + UNWIND_HINT_FUNC + RET SYM_CODE_END(return_to_handler) #endif
From: Peter Zijlstra peterz@infradead.org
commit 1f001e9da6bbf482311e45e48f53c2bd2179e59c upstream.
Use the return thunk in ftrace trampolines, if needed.
Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Signed-off-by: Borislav Petkov bp@suse.de Reviewed-by: Josh Poimboeuf jpoimboe@kernel.org Signed-off-by: Borislav Petkov bp@suse.de [cascardo: use memcpy(text_gen_insn) as there is no __text_gen_insn] Signed-off-by: Thadeu Lima de Souza Cascardo cascardo@canonical.com Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com --- arch/x86/kernel/ftrace.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index b80e38cbd49e..d096b5a1dbeb 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -309,7 +309,7 @@ union ftrace_op_code_union { } __attribute__((packed)); };
-#define RET_SIZE 1 + IS_ENABLED(CONFIG_SLS) +#define RET_SIZE (IS_ENABLED(CONFIG_RETPOLINE) ? 5 : 1 + IS_ENABLED(CONFIG_SLS))
static unsigned long create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) @@ -365,7 +365,12 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) goto fail;
ip = trampoline + size; - memcpy(ip, retq, RET_SIZE); + + /* The trampoline ends with ret(q) */ + if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) + memcpy(ip, text_gen_insn(JMP32_INSN_OPCODE, ip, &__x86_return_thunk), JMP32_INSN_SIZE); + else + memcpy(ip, retq, sizeof(retq));
/* No need to test direct calls on created trampolines */ if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {
linux-stable-mirror@lists.linaro.org
-
Ovidiu Panait