[PATCH 6.3 18/29] arm/mm: Convert to using lock_mm_and_find_vma()

Greg Kroah-Hartman
2023-06-29T18:46:35Z

From: Ben Hutchings <ben@decadent.org.uk>

commit 8b35ca3e45e35a26a21427f35d4093606e93ad0a upstream.

arm has an additional check for address < FIRST_USER_ADDRESS before
expanding the stack. Since FIRST_USER_ADDRESS is defined everywhere
(generally as 0), move that check to the generic expand_downwards().

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/arm/Kconfig | 1
arch/arm/mm/fault.c | 63 +++++++++++-----------------------------------------
mm/mmap.c | 2 -
3 files changed, 16 insertions(+), 50 deletions(-)

--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -125,6 +125,7 @@ config ARM
select HAVE_UID16
select HAVE_VIRT_CPU_ACCOUNTING_GEN
select IRQ_FORCED_THREADING
+ select LOCK_MM_AND_FIND_VMA
select MODULES_USE_ELF_REL
select NEED_DMA_MAP_STATE
select OF_EARLY_FLATTREE if OF
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -232,37 +232,11 @@ static inline bool is_permission_fault(u
return false;
}

-static vm_fault_t __kprobes
-__do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int flags,
- unsigned long vma_flags, struct pt_regs *regs)
-{
- struct vm_area_struct *vma = find_vma(mm, addr);
- if (unlikely(!vma))
- return VM_FAULT_BADMAP;
-
- if (unlikely(vma->vm_start > addr)) {
- if (!(vma->vm_flags & VM_GROWSDOWN))
- return VM_FAULT_BADMAP;
- if (addr < FIRST_USER_ADDRESS)
- return VM_FAULT_BADMAP;
- if (expand_stack(vma, addr))
- return VM_FAULT_BADMAP;
- }
-
- /*
- * ok, we have a good vm_area for this memory access, check the
- * permissions on the VMA allow for the fault which occurred.
- */
- if (!(vma->vm_flags & vma_flags))
- return VM_FAULT_BADACCESS;
-
- return handle_mm_fault(vma, addr & PAGE_MASK, flags, regs);
-}
-
static int __kprobes
do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
{
struct mm_struct *mm = current->mm;
+ struct vm_area_struct *vma;
int sig, code;
vm_fault_t fault;
unsigned int flags = FAULT_FLAG_DEFAULT;
@@ -301,31 +275,21 @@ do_page_fault(unsigned long addr, unsign

perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);

- /*
- * As per x86, we may deadlock here. However, since the kernel only
- * validly references user space from well defined areas of the code,
- * we can bug out early if this is from code which shouldn't.
- */
- if (!mmap_read_trylock(mm)) {
- if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc))
- goto no_context;
retry:
- mmap_read_lock(mm);
- } else {
- /*
- * The above down_read_trylock() might have succeeded in
- * which case, we'll have missed the might_sleep() from
- * down_read()
- */
- might_sleep();
-#ifdef CONFIG_DEBUG_VM
- if (!user_mode(regs) &&
- !search_exception_tables(regs->ARM_pc))
- goto no_context;
-#endif
+ vma = lock_mm_and_find_vma(mm, addr, regs);
+ if (unlikely(!vma)) {
+ fault = VM_FAULT_BADMAP;
+ goto bad_area;
}

- fault = __do_page_fault(mm, addr, flags, vm_flags, regs);
+ /*
+ * ok, we have a good vm_area for this memory access, check the
+ * permissions on the VMA allow for the fault which occurred.
+ */
+ if (!(vma->vm_flags & vm_flags))
+ fault = VM_FAULT_BADACCESS;
+ else
+ fault = handle_mm_fault(vma, addr & PAGE_MASK, flags, regs);

/* If we need to retry but a fatal signal is pending, handle the
* signal first. We do not need to release the mmap_lock because
@@ -356,6 +320,7 @@ retry:
if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
return 0;

+bad_area:
/*
* If we are in kernel mode at this point, we
* have no context to handle this fault with.
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1999,7 +1999,7 @@ int expand_downwards(struct vm_area_stru
int error = 0;

address &= PAGE_MASK;
- if (address < mmap_min_addr)
+ if (address < mmap_min_addr || address < FIRST_USER_ADDRESS)
return -EPERM;

/* Enforce stack_guard_gap */