[PATCH v2 1/2] dax: dax_pfn_mkwrite() truncate race check
From: Ross Zwisler <hidden>
Date: 2015-10-13 22:25:36
Also in:
linux-fsdevel, lkml, nvdimm
Subsystem:
filesystem direct access (dax), filesystems (vfs and infrastructure), the rest · Maintainers:
Dan Williams, Alexander Viro, Christian Brauner, Linus Torvalds
Update dax_pfn_mkwrite() so that it validates i_size before returning. This is necessary to ensure that the page fault has not raced with truncate and is now pointing to a region beyond the end of the current file. This change is based on a similar outstanding patch for XFS from Dave Chinner entitled "xfs: add ->pfn_mkwrite support for DAX". Signed-off-by: Ross Zwisler <redacted> Cc: Dave Chinner <david@fromorbit.com> --- fs/dax.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index 131fd35a..82be6e4 100644
--- a/fs/dax.c
+++ b/fs/dax.c@@ -693,12 +693,21 @@ EXPORT_SYMBOL_GPL(dax_pmd_fault); */ int dax_pfn_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) { - struct super_block *sb = file_inode(vma->vm_file)->i_sb; + struct inode *inode = file_inode(vma->vm_file); + struct super_block *sb = inode->i_sb; + int ret = VM_FAULT_NOPAGE; + loff_t size; sb_start_pagefault(sb); file_update_time(vma->vm_file); + + /* check that the faulting page hasn't raced with truncate */ + size = (i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; + if (vmf->pgoff >= size) + ret = VM_FAULT_SIGBUS; + sb_end_pagefault(sb); - return VM_FAULT_NOPAGE; + return ret; } EXPORT_SYMBOL_GPL(dax_pfn_mkwrite);
--
2.1.0