This is a note to let you know that I've just added the patch titled
PM: hibernate: Clean up sync_read handling in snapshot_write_next()
to the 6.5-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
pm-hibernate-clean-up-sync_read-handling-in-snapshot_write_next.patch
and it can be found in the queue-6.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From d08970df1980476f27936e24d452550f3e9e92e1 Mon Sep 17 00:00:00 2001
From: Brian Geffon <bgeffon@xxxxxxxxxx>
Date: Fri, 22 Sep 2023 12:07:04 -0400
Subject: PM: hibernate: Clean up sync_read handling in snapshot_write_next()
From: Brian Geffon <bgeffon@xxxxxxxxxx>
commit d08970df1980476f27936e24d452550f3e9e92e1 upstream.
In snapshot_write_next(), sync_read is set and unset in three different
spots unnecessiarly. As a result there is a subtle bug where the first
page after the meta data has been loaded unconditionally sets sync_read
to 0. If this first PFN was actually a highmem page, then the returned
buffer will be the global "buffer," and the page needs to be loaded
synchronously.
That is, I'm not sure we can always assume the following to be safe:
handle->buffer = get_buffer(&orig_bm, &ca);
handle->sync_read = 0;
Because get_buffer() can call get_highmem_page_buffer() which can
return 'buffer'.
The easiest way to address this is just set sync_read before
snapshot_write_next() returns if handle->buffer == buffer.
Signed-off-by: Brian Geffon <bgeffon@xxxxxxxxxx>
Fixes: 8357376d3df2 ("[PATCH] swsusp: Improve handling of highmem")
Cc: All applicable <stable@xxxxxxxxxxxxxxx>
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/power/snapshot.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -2689,8 +2689,6 @@ int snapshot_write_next(struct snapshot_
if (handle->cur > 1 && handle->cur > nr_meta_pages + nr_copy_pages)
return 0;
- handle->sync_read = 1;
-
if (!handle->cur) {
if (!buffer)
/* This makes the buffer be freed by swsusp_free() */
@@ -2726,7 +2724,6 @@ int snapshot_write_next(struct snapshot_
memory_bm_position_reset(&orig_bm);
restore_pblist = NULL;
handle->buffer = get_buffer(&orig_bm, &ca);
- handle->sync_read = 0;
if (IS_ERR(handle->buffer))
return PTR_ERR(handle->buffer);
}
@@ -2736,9 +2733,8 @@ int snapshot_write_next(struct snapshot_
handle->buffer = get_buffer(&orig_bm, &ca);
if (IS_ERR(handle->buffer))
return PTR_ERR(handle->buffer);
- if (handle->buffer != buffer)
- handle->sync_read = 0;
}
+ handle->sync_read = (handle->buffer == buffer);
handle->cur++;
return PAGE_SIZE;
}
Patches currently in stable-queue which might be from bgeffon@xxxxxxxxxx are
queue-6.5/pm-hibernate-clean-up-sync_read-handling-in-snapshot_write_next.patch
queue-6.5/pm-hibernate-use-__get_safe_page-rather-than-touching-the-list.patch
