From b2edffdd912b4205899a8efa0974dfbbc3216109 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Mon, 6 Apr 2015 17:48:54 -0400 Subject: 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 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) (limited to 'fs/aio.c') 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; -- cgit v1.2.3-59-g8ed1b