On Mon, Apr 16, 2018 at 09:55:45PM +0200, René Rebe wrote: > Hi, > > On 04/16/2018 06:48 PM, David Sterba wrote: > > The warnings are valid, there's unaligned access introduced by patch > > > > 23b5ec74943f44378b68c0edd8e210a86318ea5e > > btrfs: fix readdir deadlock with pagefault > > > > The directory entries (struct dir_entry) are copied to a temporary > > buffer as they fit, ie. no alignment, and the members accessed in > > several places. > > > > The following patch adds the proper unaligned access, only compile-tested. > > Please test and let me know, thanks! > Would have loved to immediately give it a try, however, sorry, > I forgot to mention I'm on the latest stable release -4.16.2- > on a first glance this does not look like it does just apply. > > I would re-base myself if I would not also have a glibc initialization > bug to hunt and debug, too :-/ > > If you happen to also rebase it for current -stable, ... ;-) Sure, attached a 4.16.2 version.
>From 4df58593a5a42c632f1c18ced3d6fae2196e29a9 Mon Sep 17 00:00:00 2001 From: David Sterba <dsterba@xxxxxxxx> Date: Mon, 16 Apr 2018 21:10:14 +0200 Subject: [PATCH] test readdir unaligned access --- fs/btrfs/inode.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index c7b75dd58fad..c2df7b158820 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -44,6 +44,7 @@ #include <linux/uio.h> #include <linux/magic.h> #include <linux/iversion.h> +#include <asm/unaligned.h> #include "ctree.h" #include "disk-io.h" #include "transaction.h" @@ -5951,11 +5952,13 @@ static int btrfs_filldir(void *addr, int entries, struct dir_context *ctx) struct dir_entry *entry = addr; char *name = (char *)(entry + 1); - ctx->pos = entry->offset; - if (!dir_emit(ctx, name, entry->name_len, entry->ino, - entry->type)) + ctx->pos = get_unaligned(&entry->offset); + if (!dir_emit(ctx, name, get_unaligned(&entry->name_len), + get_unaligned(&entry->ino), + get_unaligned(&entry->type))) return 1; - addr += sizeof(struct dir_entry) + entry->name_len; + addr += sizeof(struct dir_entry) + + get_unaligned(&entry->name_len); ctx->pos++; } return 0; @@ -6045,14 +6048,15 @@ static int btrfs_real_readdir(struct file *file, struct dir_context *ctx) } entry = addr; - entry->name_len = name_len; + put_unaligned(name_len, &entry->name_len); name_ptr = (char *)(entry + 1); read_extent_buffer(leaf, name_ptr, (unsigned long)(di + 1), name_len); - entry->type = btrfs_filetype_table[btrfs_dir_type(leaf, di)]; + put_unaligned(btrfs_filetype_table[btrfs_dir_type(leaf, di)], + &entry->type); btrfs_dir_item_key_to_cpu(leaf, di, &location); - entry->ino = location.objectid; - entry->offset = found_key.offset; + put_unaligned(location.objectid, &entry->ino); + put_unaligned(found_key.offset,&entry->offset); entries++; addr += sizeof(struct dir_entry) + name_len; total_len += sizeof(struct dir_entry) + name_len; -- 2.16.2
