From d082d48737c75d2b3cc1f972b8c8674c25131534 Mon Sep 17 00:00:00 2001 From: Lee Jones Date: Wed, 14 Jun 2023 17:38:54 +0100 Subject: x86/mm: Avoid using set_pgd() outside of real PGD pages KPTI keeps around two PGDs: one for userspace and another for the kernel. Among other things, set_pgd() contains infrastructure to ensure that updates to the kernel PGD are reflected in the user PGD as well. One side-effect of this is that set_pgd() expects to be passed whole pages. Unfortunately, init_trampoline_kaslr() passes in a single entry: 'trampoline_pgd_entry'. When KPTI is on, set_pgd() will update 'trampoline_pgd_entry' (an 8-Byte globally stored [.bss] variable) and will then proceed to replicate that value into the non-existent neighboring user page (located +4k away), leading to the corruption of other global [.bss] stored variables. Fix it by directly assigning 'trampoline_pgd_entry' and avoiding set_pgd(). [ dhansen: tweak subject and changelog ] Fixes: 0925dda5962e ("x86/mm/KASLR: Use only one PUD entry for real mode trampoline") Suggested-by: Dave Hansen Signed-off-by: Lee Jones Signed-off-by: Dave Hansen Cc: Link: https://lore.kernel.org/all/20230614163859.924309-1-lee@kernel.org/g --- arch/x86/mm/kaslr.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c index 557f0fe25dff..37db264866b6 100644 --- a/arch/x86/mm/kaslr.c +++ b/arch/x86/mm/kaslr.c @@ -172,10 +172,10 @@ void __meminit init_trampoline_kaslr(void) set_p4d(p4d_tramp, __p4d(_KERNPG_TABLE | __pa(pud_page_tramp))); - set_pgd(&trampoline_pgd_entry, - __pgd(_KERNPG_TABLE | __pa(p4d_page_tramp))); + trampoline_pgd_entry = + __pgd(_KERNPG_TABLE | __pa(p4d_page_tramp)); } else { - set_pgd(&trampoline_pgd_entry, - __pgd(_KERNPG_TABLE | __pa(pud_page_tramp))); + trampoline_pgd_entry = + __pgd(_KERNPG_TABLE | __pa(pud_page_tramp)); } } -- cgit v1.2.3-70-g09d2 From 85d38d5810e285d5aec7fb5283107d1da70c12a9 Mon Sep 17 00:00:00 2001 From: Dheeraj Kumar Srivastava Date: Sat, 17 Jun 2023 02:52:36 +0530 Subject: x86/apic: Fix kernel panic when booting with intremap=off and x2apic_phys When booting with "intremap=off" and "x2apic_phys" on the kernel command line, the physical x2APIC driver ends up being used even when x2APIC mode is disabled ("intremap=off" disables x2APIC mode). This happens because the first compound condition check in x2apic_phys_probe() is false due to x2apic_mode == 0 and so the following one returns true after default_acpi_madt_oem_check() having already selected the physical x2APIC driver. This results in the following panic: kernel BUG at arch/x86/kernel/apic/io_apic.c:2409! invalid opcode: 0000 [#1] PREEMPT SMP NOPTI CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.4.0-rc2-ver4.1rc2 #2 Hardware name: Dell Inc. PowerEdge R6515/07PXPY, BIOS 2.3.6 07/06/2021 RIP: 0010:setup_IO_APIC+0x9c/0xaf0 Call Trace: ? native_read_msr apic_intr_mode_init x86_late_time_init start_kernel x86_64_start_reservations x86_64_start_kernel secondary_startup_64_no_verify which is: setup_IO_APIC: apic_printk(APIC_VERBOSE, "ENABLING IO-APIC IRQs\n"); for_each_ioapic(ioapic) BUG_ON(mp_irqdomain_create(ioapic)); Return 0 to denote that x2APIC has not been enabled when probing the physical x2APIC driver. [ bp: Massage commit message heavily. ] Fixes: 9ebd680bd029 ("x86, apic: Use probe routines to simplify apic selection") Signed-off-by: Dheeraj Kumar Srivastava Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Kishon Vijay Abraham I Reviewed-by: Vasant Hegde Reviewed-by: Cyrill Gorcunov Reviewed-by: Thomas Gleixner Link: https://lore.kernel.org/r/20230616212236.1389-1-dheerajkumar.srivastava@amd.com --- arch/x86/kernel/apic/x2apic_phys.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/apic/x2apic_phys.c b/arch/x86/kernel/apic/x2apic_phys.c index 6bde05a86b4e..896bc41cb2ba 100644 --- a/arch/x86/kernel/apic/x2apic_phys.c +++ b/arch/x86/kernel/apic/x2apic_phys.c @@ -97,7 +97,10 @@ static void init_x2apic_ldr(void) static int x2apic_phys_probe(void) { - if (x2apic_mode && (x2apic_phys || x2apic_fadt_phys())) + if (!x2apic_mode) + return 0; + + if (x2apic_phys || x2apic_fadt_phys()) return 1; return apic == &apic_x2apic_phys; -- cgit v1.2.3-70-g09d2