From eec13b42d41b0f3339dcf0c4da43734427c68620 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Thu, 18 Jun 2020 11:16:45 +0100 Subject: [PATCH 1/3] ARM: 8986/1: hw_breakpoint: Don't invoke overflow handler on uaccess watchpoints Unprivileged memory accesses generated by the so-called "translated" instructions (e.g. LDRT) in kernel mode can cause user watchpoints to fire unexpectedly. In such cases, the hw_breakpoint logic will invoke the user overflow handler which will typically raise a SIGTRAP back to the current task. This is futile when returning back to the kernel because (a) the signal won't have been delivered and (b) userspace can't handle the thing anyway. Avoid invoking the user overflow handler for watchpoints triggered by kernel uaccess routines, and instead single-step over the faulting instruction as we would if no overflow handler had been installed. Cc: Fixes: f81ef4a920c8 ("ARM: 6356/1: hw-breakpoint: add ARM backend for the hw-breakpoint framework") Reported-by: Luis Machado Tested-by: Luis Machado Signed-off-by: Will Deacon Signed-off-by: Russell King --- arch/arm/kernel/hw_breakpoint.c | 27 ++++++++++++++++++++++----- 1 file changed, 22 insertions(+), 5 deletions(-) diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c index 02ca7adf5375..7fff88e61252 100644 --- a/arch/arm/kernel/hw_breakpoint.c +++ b/arch/arm/kernel/hw_breakpoint.c @@ -683,6 +683,12 @@ static void disable_single_step(struct perf_event *bp) arch_install_hw_breakpoint(bp); } +static int watchpoint_fault_on_uaccess(struct pt_regs *regs, + struct arch_hw_breakpoint *info) +{ + return !user_mode(regs) && info->ctrl.privilege == ARM_BREAKPOINT_USER; +} + static void watchpoint_handler(unsigned long addr, unsigned int fsr, struct pt_regs *regs) { @@ -742,16 +748,27 @@ static void watchpoint_handler(unsigned long addr, unsigned int fsr, } pr_debug("watchpoint fired: address = 0x%x\n", info->trigger); + + /* + * If we triggered a user watchpoint from a uaccess routine, + * then handle the stepping ourselves since userspace really + * can't help us with this. + */ + if (watchpoint_fault_on_uaccess(regs, info)) + goto step; + perf_bp_event(wp, regs); /* - * If no overflow handler is present, insert a temporary - * mismatch breakpoint so we can single-step over the - * watchpoint trigger. + * Defer stepping to the overflow handler if one is installed. + * Otherwise, insert a temporary mismatch breakpoint so that + * we can single-step over the watchpoint trigger. */ - if (is_default_overflow_handler(wp)) - enable_single_step(wp, instruction_pointer(regs)); + if (!is_default_overflow_handler(wp)) + goto unlock; +step: + enable_single_step(wp, instruction_pointer(regs)); unlock: rcu_read_unlock(); } From 4405bdf3c57ec28d606bdf5325f1167505bfdcd4 Mon Sep 17 00:00:00 2001 From: Jaedon Shin Date: Thu, 18 Jun 2020 18:15:30 +0100 Subject: [PATCH 2/3] ARM: 8987/1: VDSO: Fix incorrect clock_gettime64 __vdso_*() should be removed and fallback used if CNTCVT is not available by cntvct_functional(). __vdso_clock_gettime64 when added previous commit is using the incorrect CNTCVT value in that state. __vdso_clock_gettime64 is also added to remove it's symbol. Cc: stable@vger.kernel.org Fixes: 74d06efb9c2f ("ARM: 8932/1: Add clock_gettime64 entry point") Signed-off-by: Jaedon Shin Tested-by: Robin Murphy Signed-off-by: Robin Murphy Signed-off-by: Russell King --- arch/arm/kernel/vdso.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c index 6bfdca4769a7..fddd08a6e063 100644 --- a/arch/arm/kernel/vdso.c +++ b/arch/arm/kernel/vdso.c @@ -184,6 +184,7 @@ static void __init patch_vdso(void *ehdr) if (!cntvct_ok) { vdso_nullpatch_one(&einfo, "__vdso_gettimeofday"); vdso_nullpatch_one(&einfo, "__vdso_clock_gettime"); + vdso_nullpatch_one(&einfo, "__vdso_clock_gettime64"); } } From 5c6360ee4a0e7f62de34341ad5d3c936f49b391d Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Wed, 24 Jun 2020 08:51:49 +0100 Subject: [PATCH 3/3] ARM: 8988/1: mmu: fix crash in EFI calls due to p4d typo in create_mapping_late() Commit 84e6ffb2c49c7901 ("arm: add support for folded p4d page tables") updated create_mapping_late() to take folded P4Ds into account when creating mappings, but inverted the p4d_alloc() failure test, resulting in no mapping to be created at all. When the EFI rtc driver subsequently tries to invoke the EFI GetTime() service, the memory regions covering the EFI data structures are missing from the page tables, resulting in a crash like Unable to handle kernel paging request at virtual address 5ae0cf28 pgd = (ptrval) [5ae0cf28] *pgd=80000040205003, *pmd=00000000 Internal error: Oops: 207 [#1] SMP THUMB2 Modules linked in: CPU: 0 PID: 7 Comm: kworker/u32:0 Not tainted 5.7.0+ #92 Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 Workqueue: efi_rts_wq efi_call_rts PC is at efi_call_rts+0x94/0x294 LR is at efi_call_rts+0x83/0x294 pc : [] lr : [] psr: 30000033 sp : e6219ef0 ip : 00000000 fp : ffffe000 r10: 00000000 r9 : 00000000 r8 : 30000013 r7 : e6201dd0 r6 : e6201ddc r5 : 00000000 r4 : c181f264 r3 : 5ae0cf10 r2 : 00000001 r1 : e6201dd0 r0 : e6201ddc Flags: nzCV IRQs on FIQs on Mode SVC_32 ISA Thumb Segment none Control: 70c5383d Table: 661cc840 DAC: 00000001 Process kworker/u32:0 (pid: 7, stack limit = 0x(ptrval)) ... [] (efi_call_rts) from [] (process_one_work+0x16d/0x3d8) [] (process_one_work) from [] (worker_thread+0xfd/0x408) [] (worker_thread) from [] (kthread+0x103/0x104) ... Fixes: 84e6ffb2c49c7901 ("arm: add support for folded p4d page tables") Reviewed-by: Mike Rapoport Signed-off-by: Ard Biesheuvel Signed-off-by: Russell King --- arch/arm/mm/mmu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c index 628028bfbb92..bcd82614c25d 100644 --- a/arch/arm/mm/mmu.c +++ b/arch/arm/mm/mmu.c @@ -966,7 +966,7 @@ void __init create_mapping_late(struct mm_struct *mm, struct map_desc *md, pud_t *pud; p4d = p4d_alloc(mm, pgd_offset(mm, md->virtual), md->virtual); - if (!WARN_ON(!p4d)) + if (WARN_ON(!p4d)) return; pud = pud_alloc(mm, p4d, md->virtual); if (WARN_ON(!pud))