diff options
Diffstat (limited to 'arch/powerpc/mm/fault.c')
| -rw-r--r-- | arch/powerpc/mm/fault.c | 55 |
1 files changed, 38 insertions, 17 deletions
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index 5fc8a010fdf0..ebe97e5500ee 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c @@ -22,6 +22,7 @@ #include <linux/errno.h> #include <linux/string.h> #include <linux/types.h> +#include <linux/pagemap.h> #include <linux/ptrace.h> #include <linux/mman.h> #include <linux/mm.h> @@ -66,15 +67,11 @@ static inline bool notify_page_fault(struct pt_regs *regs) } /* - * Check whether the instruction at regs->nip is a store using + * Check whether the instruction inst is a store using * an update addressing form which will update r1. */ -static bool store_updates_sp(struct pt_regs *regs) +static bool store_updates_sp(unsigned int inst) { - unsigned int inst; - - if (get_user(inst, (unsigned int __user *)regs->nip)) - return false; /* check for 1 in the rA field */ if (((inst >> 16) & 0x1f) != 1) return false; @@ -227,20 +224,24 @@ static bool bad_kernel_fault(bool is_exec, unsigned long error_code, return is_exec || (address >= TASK_SIZE); } +// This comes from 64-bit struct rt_sigframe + __SIGNAL_FRAMESIZE +#define SIGFRAME_MAX_SIZE (4096 + 128) + static bool bad_stack_expansion(struct pt_regs *regs, unsigned long address, - struct vm_area_struct *vma, - bool store_update_sp) + struct vm_area_struct *vma, unsigned int flags, + bool *must_retry) { /* * N.B. The POWER/Open ABI allows programs to access up to * 288 bytes below the stack pointer. - * The kernel signal delivery code writes up to about 1.5kB + * The kernel signal delivery code writes a bit over 4KB * below the stack pointer (r1) before decrementing it. * The exec code can write slightly over 640kB to the stack * before setting the user r1. Thus we allow the stack to * expand to 1MB without further checks. */ if (address + 0x100000 < vma->vm_end) { + unsigned int __user *nip = (unsigned int __user *)regs->nip; /* get user regs even if this fault is in kernel mode */ struct pt_regs *uregs = current->thread.regs; if (uregs == NULL) @@ -258,8 +259,22 @@ static bool bad_stack_expansion(struct pt_regs *regs, unsigned long address, * between the last mapped region and the stack will * expand the stack rather than segfaulting. */ - if (address + 2048 < uregs->gpr[1] && !store_update_sp) - return true; + if (address + SIGFRAME_MAX_SIZE >= uregs->gpr[1]) + return false; + + if ((flags & FAULT_FLAG_WRITE) && (flags & FAULT_FLAG_USER) && + access_ok(VERIFY_READ, nip, sizeof(*nip))) { + unsigned int inst; + int res; + + pagefault_disable(); + res = __get_user_inatomic(inst, nip); + pagefault_enable(); + if (!res) + return !store_updates_sp(inst); + *must_retry = true; + } + return true; } return false; } @@ -392,7 +407,7 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address, int is_user = user_mode(regs); int is_write = page_fault_is_write(error_code); int fault, major = 0; - bool store_update_sp = false; + bool must_retry = false; if (notify_page_fault(regs)) return 0; @@ -439,9 +454,6 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address, * can result in fault, which will cause a deadlock when called with * mmap_sem held */ - if (is_write && is_user) - store_update_sp = store_updates_sp(regs); - if (is_user) flags |= FAULT_FLAG_USER; if (is_write) @@ -488,8 +500,17 @@ retry: return bad_area(regs, address); /* The stack is being expanded, check if it's valid */ - if (unlikely(bad_stack_expansion(regs, address, vma, store_update_sp))) - return bad_area(regs, address); + if (unlikely(bad_stack_expansion(regs, address, vma, flags, + &must_retry))) { + if (!must_retry) + return bad_area(regs, address); + + up_read(&mm->mmap_sem); + if (fault_in_pages_readable((const char __user *)regs->nip, + sizeof(unsigned int))) + return bad_area_nosemaphore(regs, address); + goto retry; + } /* Try to expand it */ if (unlikely(expand_stack(vma, address))) |