From 71f5344f477c3381dc2a61a2f9086bd1a8e6afd5 Mon Sep 17 00:00:00 2001 From: Brian Geffon Date: Fri, 22 Sep 2023 12:07:04 -0400 Subject: [PATCH] PM: hibernate: Clean up sync_read handling in snapshot_write_next() 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 Fixes: 8357376d3df2 ("[PATCH] swsusp: Improve handling of highmem") Cc: All applicable [ rjw: Subject and changelog edits ] Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman --- kernel/power/snapshot.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c index 44721c640f86..2b063e0a15c6 100644 --- a/kernel/power/snapshot.c +++ b/kernel/power/snapshot.c @@ -2629,8 +2629,6 @@ int snapshot_write_next(struct snapshot_handle *handle) 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() */ @@ -2666,7 +2664,6 @@ int snapshot_write_next(struct snapshot_handle *handle) 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); } @@ -2676,9 +2673,8 @@ int snapshot_write_next(struct snapshot_handle *handle) 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; }