From b2edffdd912b4205899a8efa0974dfbbc3216109 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Mon, 6 Apr 2015 17:48:54 -0400 Subject: [PATCH] fix mremap() vs. ioctx_kill() race teach ->mremap() method to return an error and have it fail for aio mappings in process of being killed Note that in case of ->mremap() failure we need to undo move_page_tables() we'd already done; we could call ->mremap() first, but then the failure of move_page_tables() would require undoing whatever _successful_ ->mremap() has done, which would be a lot more headache in general. Signed-off-by: Al Viro --- fs/aio.c | 17 +++++++++++------ include/linux/fs.h | 2 +- mm/mremap.c | 10 ++++++++-- 3 files changed, 20 insertions(+), 9 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index f8e52a1854c1..58c33dcfb6ca 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -278,11 +278,11 @@ static int aio_ring_mmap(struct file *file, struct vm_area_struct *vma) return 0; } -static void aio_ring_remap(struct file *file, struct vm_area_struct *vma) +static int aio_ring_remap(struct file *file, struct vm_area_struct *vma) { struct mm_struct *mm = vma->vm_mm; struct kioctx_table *table; - int i; + int i, res = -EINVAL; spin_lock(&mm->ioctx_lock); rcu_read_lock(); @@ -292,13 +292,17 @@ static void aio_ring_remap(struct file *file, struct vm_area_struct *vma) ctx = table->table[i]; if (ctx && ctx->aio_ring_file == file) { - ctx->user_id = ctx->mmap_base = vma->vm_start; + if (!atomic_read(&ctx->dead)) { + ctx->user_id = ctx->mmap_base = vma->vm_start; + res = 0; + } break; } } rcu_read_unlock(); spin_unlock(&mm->ioctx_lock); + return res; } static const struct file_operations aio_ring_fops = { @@ -748,11 +752,12 @@ static int kill_ioctx(struct mm_struct *mm, struct kioctx *ctx, { struct kioctx_table *table; - if (atomic_xchg(&ctx->dead, 1)) + spin_lock(&mm->ioctx_lock); + if (atomic_xchg(&ctx->dead, 1)) { + spin_unlock(&mm->ioctx_lock); return -EINVAL; + } - - spin_lock(&mm->ioctx_lock); table = rcu_dereference_raw(mm->ioctx_table); WARN_ON(ctx != table->table[ctx->id]); table->table[ctx->id] = NULL; diff --git a/include/linux/fs.h b/include/linux/fs.h index f4131e8ead74..52cc4492cb3a 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1549,7 +1549,7 @@ struct file_operations { long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long); long (*compat_ioctl) (struct file *, unsigned int, unsigned long); int (*mmap) (struct file *, struct vm_area_struct *); - void (*mremap)(struct file *, struct vm_area_struct *); + int (*mremap)(struct file *, struct vm_area_struct *); int (*open) (struct inode *, struct file *); int (*flush) (struct file *, fl_owner_t id); int (*release) (struct inode *, struct file *); diff --git a/mm/mremap.c b/mm/mremap.c index 57dadc025c64..2dc44b1cb1df 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -286,8 +286,14 @@ static unsigned long move_vma(struct vm_area_struct *vma, old_len = new_len; old_addr = new_addr; new_addr = -ENOMEM; - } else if (vma->vm_file && vma->vm_file->f_op->mremap) - vma->vm_file->f_op->mremap(vma->vm_file, new_vma); + } else if (vma->vm_file && vma->vm_file->f_op->mremap) { + err = vma->vm_file->f_op->mremap(vma->vm_file, new_vma); + if (err < 0) { + move_page_tables(new_vma, new_addr, vma, old_addr, + moved_len, true); + return err; + } + } /* Conceal VM_ACCOUNT so old reservation is not undone */ if (vm_flags & VM_ACCOUNT) { -- 2.20.1