4.11-stable review patch. If anyone has any objections, please let me know.
------------------ From: Kristina Martsenko <[email protected]> commit 81cddd65b5c82758ea5571a25e31ff6f1f89ff02 upstream. When we emulate userspace cache maintenance in the kernel, we can currently send the task a SIGSEGV even though the maintenance was done on a valid address. This happens if the address has a non-zero address tag, and happens to not be mapped in. When we get the address from a user register, we don't currently remove the address tag before performing cache maintenance on it. If the maintenance faults, we end up in either __do_page_fault, where find_vma can't find the VMA if the address has a tag, or in do_translation_fault, where the tagged address will appear to be above TASK_SIZE. In both cases, the address is not mapped in, and the task is sent a SIGSEGV. This patch removes the tag from the address before using it. With this patch, the fault is handled correctly, the address gets mapped in, and the cache maintenance succeeds. As a second bug, if cache maintenance (correctly) fails on an invalid tagged address, the address gets passed into arm64_notify_segfault, where find_vma fails to find the VMA due to the tag, and the wrong si_code may be sent as part of the siginfo_t of the segfault. With this patch, the correct si_code is sent. Fixes: 7dd01aef0557 ("arm64: trap userspace "dc cvau" cache operation on errata-affected core") Acked-by: Will Deacon <[email protected]> Signed-off-by: Kristina Martsenko <[email protected]> Signed-off-by: Catalin Marinas <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/arm64/kernel/traps.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -443,7 +443,7 @@ int cpu_enable_cache_maint_trap(void *__ } #define __user_cache_maint(insn, address, res) \ - if (untagged_addr(address) >= user_addr_max()) { \ + if (address >= user_addr_max()) { \ res = -EFAULT; \ } else { \ uaccess_ttbr0_enable(); \ @@ -469,7 +469,7 @@ static void user_cache_maint_handler(uns int crm = (esr & ESR_ELx_SYS64_ISS_CRM_MASK) >> ESR_ELx_SYS64_ISS_CRM_SHIFT; int ret = 0; - address = pt_regs_read_reg(regs, rt); + address = untagged_addr(pt_regs_read_reg(regs, rt)); switch (crm) { case ESR_ELx_SYS64_ISS_CRM_DC_CVAU: /* DC CVAU, gets promoted */
