From: Jeff Layton Date: Wed, 12 Dec 2012 16:38:44 +0000 (-0500) Subject: nfs: don't zero out the rest of the page if we hit the EOF on a DIO READ X-Git-Tag: Ubuntu-5.4-5.4.0-11.14~17566^2~16 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=67fad106a219e083c91c79695bd1807dde1bf7b9;p=mirror_ubuntu-focal-kernel.git nfs: don't zero out the rest of the page if we hit the EOF on a DIO READ Eryu provided a test program that would segfault when attempting to read past the EOF on file that was opened O_DIRECT. The buffer given to the read() call was on the stack, and when he attempted to read past it it would scribble over the rest of the stack page. If we hit the end of the file on a DIO READ request, then we don't want to zero out the rest of the buffer. These aren't pagecache pages after all, and there's no guarantee that the buffers that were passed in represent entire pages. Cc: # v3.5+ Cc: Fred Isaman Reported-by: Eryu Guan Signed-off-by: Jeff Layton Signed-off-by: Trond Myklebust --- diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c index cae26cbd59ee..594f4e7e0b9a 100644 --- a/fs/nfs/direct.c +++ b/fs/nfs/direct.c @@ -266,14 +266,6 @@ static void nfs_direct_read_completion(struct nfs_pgio_header *hdr) struct nfs_page *req = nfs_list_entry(hdr->pages.next); struct page *page = req->wb_page; - if (test_bit(NFS_IOHDR_EOF, &hdr->flags)) { - if (bytes > hdr->good_bytes) - zero_user(page, 0, PAGE_SIZE); - else if (hdr->good_bytes - bytes < PAGE_SIZE) - zero_user_segment(page, - hdr->good_bytes & ~PAGE_MASK, - PAGE_SIZE); - } if (!PageCompound(page)) { if (test_bit(NFS_IOHDR_ERROR, &hdr->flags)) { if (bytes < hdr->good_bytes)