From 611d0a95d46b0977a530b4d538948c69d447b001 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Mon, 11 May 2020 10:39:24 +0900 Subject: bootconfig: Fix to prevent warning message if no bootconfig option Commit de462e5f1071 ("bootconfig: Fix to remove bootconfig data from initrd while boot") causes a cosmetic regression on dmesg, which warns "no bootconfig data" message without bootconfig cmdline option. Fix setup_boot_config() by moving no bootconfig check after commandline option check. Link: http://lkml.kernel.org/r/9b1ba335-071d-c983-89a4-2677b522dcc8@molgen.mpg.de Link: http://lkml.kernel.org/r/158916116468.21787.14558782332170588206.stgit@devnote2 Fixes: de462e5f1071 ("bootconfig: Fix to remove bootconfig data from initrd while boot") Reported-by: Paul Menzel Reviewed-by: Paul Menzel Signed-off-by: Masami Hiramatsu Signed-off-by: Steven Rostedt (VMware) --- init/main.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) (limited to 'init') diff --git a/init/main.c b/init/main.c index 1a5da2c2660c..5803ecb411ab 100644 --- a/init/main.c +++ b/init/main.c @@ -400,9 +400,8 @@ static void __init setup_boot_config(const char *cmdline) char *data, *copy; int ret; + /* Cut out the bootconfig data even if we have no bootconfig option */ data = get_boot_config_from_initrd(&size, &csum); - if (!data) - goto not_found; strlcpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE); parse_args("bootconfig", tmp_cmdline, NULL, 0, 0, 0, NULL, @@ -411,6 +410,11 @@ static void __init setup_boot_config(const char *cmdline) if (!bootconfig_found) return; + if (!data) { + pr_err("'bootconfig' found on command line, but no bootconfig found\n"); + return; + } + if (size >= XBC_DATA_MAX) { pr_err("bootconfig size %d greater than max size %d\n", size, XBC_DATA_MAX); @@ -446,8 +450,6 @@ static void __init setup_boot_config(const char *cmdline) extra_init_args = xbc_make_cmdline("init"); } return; -not_found: - pr_err("'bootconfig' found on command line, but no bootconfig found\n"); } #else -- cgit v1.2.3 From a9a3ed1eff3601b63aea4fb462d8b3b92c7c1e7e Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Wed, 22 Apr 2020 18:11:30 +0200 Subject: x86: Fix early boot crash on gcc-10, third try MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit ... or the odyssey of trying to disable the stack protector for the function which generates the stack canary value. The whole story started with Sergei reporting a boot crash with a kernel built with gcc-10: Kernel panic — not syncing: stack-protector: Kernel stack is corrupted in: start_secondary CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.6.0-rc5—00235—gfffb08b37df9 #139 Hardware name: Gigabyte Technology Co., Ltd. To be filled by O.E.M./H77M—D3H, BIOS F12 11/14/2013 Call Trace: dump_stack panic ? start_secondary __stack_chk_fail start_secondary secondary_startup_64 -—-[ end Kernel panic — not syncing: stack—protector: Kernel stack is corrupted in: start_secondary This happens because gcc-10 tail-call optimizes the last function call in start_secondary() - cpu_startup_entry() - and thus emits a stack canary check which fails because the canary value changes after the boot_init_stack_canary() call. To fix that, the initial attempt was to mark the one function which generates the stack canary with: __attribute__((optimize("-fno-stack-protector"))) ... start_secondary(void *unused) however, using the optimize attribute doesn't work cumulatively as the attribute does not add to but rather replaces previously supplied optimization options - roughly all -fxxx options. The key one among them being -fno-omit-frame-pointer and thus leading to not present frame pointer - frame pointer which the kernel needs. The next attempt to prevent compilers from tail-call optimizing the last function call cpu_startup_entry(), shy of carving out start_secondary() into a separate compilation unit and building it with -fno-stack-protector, was to add an empty asm(""). This current solution was short and sweet, and reportedly, is supported by both compilers but we didn't get very far this time: future (LTO?) optimization passes could potentially eliminate this, which leads us to the third attempt: having an actual memory barrier there which the compiler cannot ignore or move around etc. That should hold for a long time, but hey we said that about the other two solutions too so... Reported-by: Sergei Trofimovich Signed-off-by: Borislav Petkov Tested-by: Kalle Valo Cc: Link: https://lkml.kernel.org/r/20200314164451.346497-1-slyfox@gentoo.org --- arch/x86/include/asm/stackprotector.h | 7 ++++++- arch/x86/kernel/smpboot.c | 8 ++++++++ arch/x86/xen/smp_pv.c | 1 + include/linux/compiler.h | 6 ++++++ init/main.c | 2 ++ 5 files changed, 23 insertions(+), 1 deletion(-) (limited to 'init') diff --git a/arch/x86/include/asm/stackprotector.h b/arch/x86/include/asm/stackprotector.h index 91e29b6a86a5..9804a7957f4e 100644 --- a/arch/x86/include/asm/stackprotector.h +++ b/arch/x86/include/asm/stackprotector.h @@ -55,8 +55,13 @@ /* * Initialize the stackprotector canary value. * - * NOTE: this must only be called from functions that never return, + * NOTE: this must only be called from functions that never return * and it must always be inlined. + * + * In addition, it should be called from a compilation unit for which + * stack protector is disabled. Alternatively, the caller should not end + * with a function call which gets tail-call optimized as that would + * lead to checking a modified canary value. */ static __always_inline void boot_init_stack_canary(void) { diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 8c89e4d9ad28..2f24c334a938 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -266,6 +266,14 @@ static void notrace start_secondary(void *unused) wmb(); cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); + + /* + * Prevent tail call to cpu_startup_entry() because the stack protector + * guard has been changed a couple of function calls up, in + * boot_init_stack_canary() and must not be checked before tail calling + * another function. + */ + prevent_tail_call_optimization(); } /** diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c index 8fb8a50a28b4..f2adb63b2d7c 100644 --- a/arch/x86/xen/smp_pv.c +++ b/arch/x86/xen/smp_pv.c @@ -93,6 +93,7 @@ asmlinkage __visible void cpu_bringup_and_idle(void) cpu_bringup(); boot_init_stack_canary(); cpu_startup_entry(CPUHP_AP_ONLINE_IDLE); + prevent_tail_call_optimization(); } void xen_smp_intr_free_pv(unsigned int cpu) diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 034b0a644efc..448c91bf543b 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -356,4 +356,10 @@ static inline void *offset_to_ptr(const int *off) /* &a[0] degrades to a pointer: a different type from an array */ #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0])) +/* + * This is needed in functions which generate the stack canary, see + * arch/x86/kernel/smpboot.c::start_secondary() for an example. + */ +#define prevent_tail_call_optimization() mb() + #endif /* __LINUX_COMPILER_H */ diff --git a/init/main.c b/init/main.c index 1a5da2c2660c..ad3812b5ae65 100644 --- a/init/main.c +++ b/init/main.c @@ -1036,6 +1036,8 @@ asmlinkage __visible void __init start_kernel(void) /* Do the rest non-__init'ed, we're now alive */ arch_call_rest_init(); + + prevent_tail_call_optimization(); } /* Call all constructor functions linked into the kernel. */ -- cgit v1.2.3 From 0ebeea8ca8a4d1d453ad299aef0507dab04f6e8d Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Fri, 15 May 2020 12:11:16 +0200 Subject: bpf: Restrict bpf_probe_read{, str}() only to archs where they work Given the legacy bpf_probe_read{,str}() BPF helpers are broken on archs with overlapping address ranges, we should really take the next step to disable them from BPF use there. To generally fix the situation, we've recently added new helper variants bpf_probe_read_{user,kernel}() and bpf_probe_read_{user,kernel}_str(). For details on them, see 6ae08ae3dea2 ("bpf: Add probe_read_{user, kernel} and probe_read_{user,kernel}_str helpers"). Given bpf_probe_read{,str}() have been around for ~5 years by now, there are plenty of users at least on x86 still relying on them today, so we cannot remove them entirely w/o breaking the BPF tracing ecosystem. However, their use should be restricted to archs with non-overlapping address ranges where they are working in their current form. Therefore, move this behind a CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE and have x86, arm64, arm select it (other archs supporting it can follow-up on it as well). For the remaining archs, they can workaround easily by relying on the feature probe from bpftool which spills out defines that can be used out of BPF C code to implement the drop-in replacement for old/new kernels via: bpftool feature probe macro Suggested-by: Linus Torvalds Signed-off-by: Daniel Borkmann Signed-off-by: Alexei Starovoitov Reviewed-by: Masami Hiramatsu Acked-by: Linus Torvalds Cc: Brendan Gregg Cc: Christoph Hellwig Link: https://lore.kernel.org/bpf/20200515101118.6508-2-daniel@iogearbox.net --- arch/arm/Kconfig | 1 + arch/arm64/Kconfig | 1 + arch/x86/Kconfig | 1 + init/Kconfig | 3 +++ kernel/trace/bpf_trace.c | 6 ++++-- 5 files changed, 10 insertions(+), 2 deletions(-) (limited to 'init') diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 66a04f6f4775..c77c93c485a0 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -12,6 +12,7 @@ config ARM select ARCH_HAS_KEEPINITRD select ARCH_HAS_KCOV select ARCH_HAS_MEMBARRIER_SYNC_CORE + select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE select ARCH_HAS_PTE_SPECIAL if ARM_LPAE select ARCH_HAS_PHYS_TO_DMA select ARCH_HAS_SETUP_DMA_OPS diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 40fb05d96c60..5d513f461957 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -20,6 +20,7 @@ config ARM64 select ARCH_HAS_KCOV select ARCH_HAS_KEEPINITRD select ARCH_HAS_MEMBARRIER_SYNC_CORE + select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE select ARCH_HAS_PTE_DEVMAP select ARCH_HAS_PTE_SPECIAL select ARCH_HAS_SETUP_DMA_OPS diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 1197b5596d5a..2d3f963fd6f1 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -68,6 +68,7 @@ config X86 select ARCH_HAS_KCOV if X86_64 select ARCH_HAS_MEM_ENCRYPT select ARCH_HAS_MEMBARRIER_SYNC_CORE + select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE select ARCH_HAS_PMEM_API if X86_64 select ARCH_HAS_PTE_DEVMAP if X86_64 select ARCH_HAS_PTE_SPECIAL diff --git a/init/Kconfig b/init/Kconfig index 9e22ee8fbd75..6fd13a051342 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -2279,6 +2279,9 @@ config ASN1 source "kernel/Kconfig.locks" +config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE + bool + config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE bool diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index ca1796747a77..b83bdaa31c7b 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -825,14 +825,16 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_probe_read_user_proto; case BPF_FUNC_probe_read_kernel: return &bpf_probe_read_kernel_proto; - case BPF_FUNC_probe_read: - return &bpf_probe_read_compat_proto; case BPF_FUNC_probe_read_user_str: return &bpf_probe_read_user_str_proto; case BPF_FUNC_probe_read_kernel_str: return &bpf_probe_read_kernel_str_proto; +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE + case BPF_FUNC_probe_read: + return &bpf_probe_read_compat_proto; case BPF_FUNC_probe_read_str: return &bpf_probe_read_compat_str_proto; +#endif #ifdef CONFIG_CGROUPS case BPF_FUNC_get_current_cgroup_id: return &bpf_get_current_cgroup_id_proto; -- cgit v1.2.3