mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-23 17:30:02 +00:00
![Phillip Lougher](/assets/img/avatar_default.png)
Patch series "squashfs: fix some regressions introduced in the readahead
code".
This patchset fixes 3 regressions introduced by the recent readahead code
changes. The first regression is causing "snaps" to randomly fail after a
couple of hours or days, which how the regression came to light.
This patch (of 3):
If a file isn't a whole multiple of the page size, the last page will have
trailing bytes unfilled.
There was a mistake in the readahead code which did this. In particular
it incorrectly assumed that the last page in the readahead page array
(page[nr_pages - 1]) will always contain the last page in the block, which
if we're at file end, will be the page that needs to be zero filled.
But the readahead code may not return the last page in the block, which
means it is unmapped and will be skipped by the decompressors (a temporary
buffer used).
In this case the zero filling code will zero out the wrong page, leading
to data corruption.
Fix this by by extending the "page actor" to return the last page if
present, or NULL if a temporary buffer was used.
Link: https://lkml.kernel.org/r/20221020223616.7571-1-phillip@squashfs.org.uk
Link: https://lkml.kernel.org/r/20221020223616.7571-2-phillip@squashfs.org.uk
Fixes: 8fc78b6fe2
("squashfs: implement readahead")
Link: https://lore.kernel.org/lkml/b0c258c3-6dcf-aade-efc4-d62a8b3a1ce2@alu.unizg.hr/
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Reported-by: Mirsad Goran Todorovac <mirsad.todorovac@alu.unizg.hr>
Tested-by: Mirsad Goran Todorovac <mirsad.todorovac@alu.unizg.hr>
Tested-by: Slade Watkins <srw@sladewatkins.net>
Tested-by: Bagas Sanjaya <bagasdotme@gmail.com>
Reported-by: Marc Miltenberger <marcmiltenberger@gmail.com>
Cc: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
Cc: Hsin-Yi Wang <hsinyi@chromium.org>
Cc: Thorsten Leemhuis <regressions@leemhuis.info>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
136 lines
3.5 KiB
C
136 lines
3.5 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
|
|
/*
|
|
* Copyright (c) 2013
|
|
* Phillip Lougher <phillip@squashfs.org.uk>
|
|
*/
|
|
|
|
#include <linux/kernel.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/pagemap.h>
|
|
#include "squashfs_fs_sb.h"
|
|
#include "decompressor.h"
|
|
#include "page_actor.h"
|
|
|
|
/*
|
|
* This file contains implementations of page_actor for decompressing into
|
|
* an intermediate buffer, and for decompressing directly into the
|
|
* page cache.
|
|
*
|
|
* Calling code should avoid sleeping between calls to squashfs_first_page()
|
|
* and squashfs_finish_page().
|
|
*/
|
|
|
|
/* Implementation of page_actor for decompressing into intermediate buffer */
|
|
static void *cache_first_page(struct squashfs_page_actor *actor)
|
|
{
|
|
actor->next_page = 1;
|
|
return actor->buffer[0];
|
|
}
|
|
|
|
static void *cache_next_page(struct squashfs_page_actor *actor)
|
|
{
|
|
if (actor->next_page == actor->pages)
|
|
return NULL;
|
|
|
|
return actor->buffer[actor->next_page++];
|
|
}
|
|
|
|
static void cache_finish_page(struct squashfs_page_actor *actor)
|
|
{
|
|
/* empty */
|
|
}
|
|
|
|
struct squashfs_page_actor *squashfs_page_actor_init(void **buffer,
|
|
int pages, int length)
|
|
{
|
|
struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL);
|
|
|
|
if (actor == NULL)
|
|
return NULL;
|
|
|
|
actor->length = length ? : pages * PAGE_SIZE;
|
|
actor->buffer = buffer;
|
|
actor->pages = pages;
|
|
actor->next_page = 0;
|
|
actor->tmp_buffer = NULL;
|
|
actor->squashfs_first_page = cache_first_page;
|
|
actor->squashfs_next_page = cache_next_page;
|
|
actor->squashfs_finish_page = cache_finish_page;
|
|
return actor;
|
|
}
|
|
|
|
/* Implementation of page_actor for decompressing directly into page cache. */
|
|
static void *handle_next_page(struct squashfs_page_actor *actor)
|
|
{
|
|
int max_pages = (actor->length + PAGE_SIZE - 1) >> PAGE_SHIFT;
|
|
|
|
if (actor->returned_pages == max_pages)
|
|
return NULL;
|
|
|
|
if ((actor->next_page == actor->pages) ||
|
|
(actor->next_index != actor->page[actor->next_page]->index)) {
|
|
actor->next_index++;
|
|
actor->returned_pages++;
|
|
actor->last_page = NULL;
|
|
return actor->alloc_buffer ? actor->tmp_buffer : ERR_PTR(-ENOMEM);
|
|
}
|
|
|
|
actor->next_index++;
|
|
actor->returned_pages++;
|
|
actor->last_page = actor->page[actor->next_page];
|
|
return actor->pageaddr = kmap_local_page(actor->page[actor->next_page++]);
|
|
}
|
|
|
|
static void *direct_first_page(struct squashfs_page_actor *actor)
|
|
{
|
|
return handle_next_page(actor);
|
|
}
|
|
|
|
static void *direct_next_page(struct squashfs_page_actor *actor)
|
|
{
|
|
if (actor->pageaddr) {
|
|
kunmap_local(actor->pageaddr);
|
|
actor->pageaddr = NULL;
|
|
}
|
|
|
|
return handle_next_page(actor);
|
|
}
|
|
|
|
static void direct_finish_page(struct squashfs_page_actor *actor)
|
|
{
|
|
if (actor->pageaddr)
|
|
kunmap_local(actor->pageaddr);
|
|
}
|
|
|
|
struct squashfs_page_actor *squashfs_page_actor_init_special(struct squashfs_sb_info *msblk,
|
|
struct page **page, int pages, int length)
|
|
{
|
|
struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL);
|
|
|
|
if (actor == NULL)
|
|
return NULL;
|
|
|
|
if (msblk->decompressor->alloc_buffer) {
|
|
actor->tmp_buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
|
|
|
|
if (actor->tmp_buffer == NULL) {
|
|
kfree(actor);
|
|
return NULL;
|
|
}
|
|
} else
|
|
actor->tmp_buffer = NULL;
|
|
|
|
actor->length = length ? : pages * PAGE_SIZE;
|
|
actor->page = page;
|
|
actor->pages = pages;
|
|
actor->next_page = 0;
|
|
actor->returned_pages = 0;
|
|
actor->next_index = page[0]->index & ~((1 << (msblk->block_log - PAGE_SHIFT)) - 1);
|
|
actor->pageaddr = NULL;
|
|
actor->last_page = NULL;
|
|
actor->alloc_buffer = msblk->decompressor->alloc_buffer;
|
|
actor->squashfs_first_page = direct_first_page;
|
|
actor->squashfs_next_page = direct_next_page;
|
|
actor->squashfs_finish_page = direct_finish_page;
|
|
return actor;
|
|
}
|