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Message-Id: <20210611180242.711399-17-dima@arista.com>
Date: Fri, 11 Jun 2021 19:02:35 +0100
From: Dmitry Safonov <dima@...sta.com>
To: linux-kernel@...r.kernel.org
Cc: Dmitry Safonov <0x7f454c46@...il.com>,
Dmitry Safonov <dima@...sta.com>,
Alexander Viro <viro@...iv.linux.org.uk>,
Andrew Morton <akpm@...ux-foundation.org>,
Andy Lutomirski <luto@...nel.org>,
Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
Catalin Marinas <catalin.marinas@....com>,
Christophe Leroy <christophe.leroy@...roup.eu>,
Guo Ren <guoren@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
Ingo Molnar <mingo@...hat.com>,
Oleg Nesterov <oleg@...hat.com>,
Russell King <linux@...linux.org.uk>,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
Thomas Gleixner <tglx@...utronix.de>,
Vincenzo Frascino <vincenzo.frascino@....com>,
Will Deacon <will@...nel.org>, x86@...nel.org,
linux-mips@...r.kernel.org
Subject: [PATCH v3 16/23] mm: Add vdso_base in mm_struct
Instead of having every architecture to define vdso_base/vdso_addr etc,
provide a generic mechanism to track vdso_base for landing in userspace.
It'll minimize per-architecture difference, the number of callbacks to
provide.
Originally, it started from thread [1] where the need for .close()
callback on vm_special_mapping was pointed, this generic code besides
removing duplicated .mremap() callbacks provides a cheaper way to
support munmap() on vdso mappings without introducing .close() callbacks
for every architecture (which would bring even more code duplication).
[1]: https://lore.kernel.org/linux-arch/CAJwJo6ZANqYkSHbQ+3b+Fi_VT80MtrzEV5yreQAWx-L8j8x2zA@mail.gmail.com/
Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc: linux-mips@...r.kernel.org
Signed-off-by: Dmitry Safonov <dima@...sta.com>
---
arch/Kconfig | 3 +++
arch/x86/kernel/cpu/resctrl/pseudo_lock.c | 3 ++-
fs/aio.c | 3 ++-
include/linux/mm.h | 3 ++-
include/linux/mm_types.h | 17 +++++++++++++++++
kernel/fork.c | 1 +
mm/mmap.c | 19 ++++++++++++++++++-
mm/mremap.c | 2 +-
8 files changed, 46 insertions(+), 5 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index c45b770d3579..0e648a1ae412 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1235,6 +1235,9 @@ config HAVE_SPARSE_SYSCALL_NR
config ARCH_HAS_VDSO_DATA
bool
+config ARCH_HAS_VDSO_BASE
+ bool
+
config HAVE_STATIC_CALL
bool
diff --git a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
index 05a89e33fde2..5ab191855816 100644
--- a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
+++ b/arch/x86/kernel/cpu/resctrl/pseudo_lock.c
@@ -1458,7 +1458,8 @@ static int pseudo_lock_dev_release(struct inode *inode, struct file *filp)
return 0;
}
-static int pseudo_lock_dev_mremap(struct vm_area_struct *area)
+static int pseudo_lock_dev_mremap(struct vm_area_struct *old_vma,
+ struct vm_area_struct *new_vma)
{
/* Not supported */
return -EINVAL;
diff --git a/fs/aio.c b/fs/aio.c
index 76ce0cc3ee4e..0b27e9300d0f 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -323,7 +323,8 @@ static void aio_free_ring(struct kioctx *ctx)
}
}
-static int aio_ring_mremap(struct vm_area_struct *vma)
+static int aio_ring_mremap(struct vm_area_struct *old_vma,
+ struct vm_area_struct *vma)
{
struct file *file = vma->vm_file;
struct mm_struct *mm = vma->vm_mm;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index c274f75efcf9..6ef91b337f9d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -589,7 +589,8 @@ struct vm_operations_struct {
void (*close)(struct vm_area_struct * area);
/* Called any time before splitting to check if it's allowed */
int (*may_split)(struct vm_area_struct *area, unsigned long addr);
- int (*mremap)(struct vm_area_struct *area);
+ int (*mremap)(struct vm_area_struct *old_vma,
+ struct vm_area_struct *new_vma);
/*
* Called by mprotect() to make driver-specific permission
* checks before mprotect() is finalised. The VMA must not
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index e9c5f2051f08..49ad34410132 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -497,6 +497,16 @@ struct mm_struct {
/* Architecture-specific MM context */
mm_context_t context;
+#ifdef CONFIG_ARCH_HAS_VDSO_BASE
+ /*
+ * Address of special mapping VMA to land after processing
+ * a signal. Reads are unprotected: if a thread unmaps or
+ * mremaps the mapping while another thread is processing
+ * a signal, it can segfault while landing.
+ */
+ void __user *vdso_base;
+#endif
+#define UNMAPPED_VDSO_BASE TASK_SIZE_MAX
unsigned long flags; /* Must use atomic bitops to access */
@@ -598,6 +608,13 @@ static inline void init_tlb_flush_pending(struct mm_struct *mm)
atomic_set(&mm->tlb_flush_pending, 0);
}
+static inline void init_vdso_base(struct mm_struct *mm)
+{
+#ifdef CONFIG_ARCH_HAS_VDSO_BASE
+ mm->vdso_base = (void __user *)UNMAPPED_VDSO_BASE;
+#endif
+}
+
static inline void inc_tlb_flush_pending(struct mm_struct *mm)
{
atomic_inc(&mm->tlb_flush_pending);
diff --git a/kernel/fork.c b/kernel/fork.c
index dc06afd725cb..eb4ad74d042e 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1082,6 +1082,7 @@ struct mm_struct *mm_alloc(void)
return NULL;
memset(mm, 0, sizeof(*mm));
+ init_vdso_base(mm);
return mm_init(mm, current, current_user_ns());
}
diff --git a/mm/mmap.c b/mm/mmap.c
index 4f0d62409b1c..5d1ffce51119 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3381,11 +3381,25 @@ void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
static vm_fault_t special_mapping_fault(struct vm_fault *vmf);
+static void update_vdso_base(struct vm_area_struct *old_vma,
+ unsigned long new_addr)
+{
+#ifdef CONFIG_ARCH_HAS_VDSO_BASE
+ struct mm_struct *mm = old_vma->vm_mm;
+
+ if (WARN_ON_ONCE(!mm))
+ return;
+ if (old_vma->vm_start == (unsigned long)mm->vdso_base)
+ mm->vdso_base = (void __user *)new_addr;
+#endif
+}
+
/*
* Having a close hook prevents vma merging regardless of flags.
*/
static void special_mapping_close(struct vm_area_struct *vma)
{
+ update_vdso_base(vma, UNMAPPED_VDSO_BASE);
}
static const char *special_mapping_name(struct vm_area_struct *vma)
@@ -3393,7 +3407,8 @@ static const char *special_mapping_name(struct vm_area_struct *vma)
return ((struct vm_special_mapping *)vma->vm_private_data)->name;
}
-static int special_mapping_mremap(struct vm_area_struct *new_vma)
+static int special_mapping_mremap(struct vm_area_struct *old_vma,
+ struct vm_area_struct *new_vma)
{
struct vm_special_mapping *sm = new_vma->vm_private_data;
@@ -3403,6 +3418,8 @@ static int special_mapping_mremap(struct vm_area_struct *new_vma)
if (sm->mremap)
sm->mremap(sm, new_vma);
+ update_vdso_base(old_vma, new_vma->vm_start);
+
return 0;
}
diff --git a/mm/mremap.c b/mm/mremap.c
index 47c255b60150..d28ba49d607c 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -545,7 +545,7 @@ static unsigned long move_vma(struct vm_area_struct *vma,
if (moved_len < old_len) {
err = -ENOMEM;
} else if (vma->vm_ops && vma->vm_ops->mremap) {
- err = vma->vm_ops->mremap(new_vma);
+ err = vma->vm_ops->mremap(vma, new_vma);
}
if (unlikely(err)) {
--
2.31.1
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