From f74e325f55c1661e3ac39f24e1d72393b13fc52f Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Fri, 30 Aug 2024 16:35:48 +0930 Subject: [PATCH] btrfs: subpage: fix the bitmap dump which can cause bitmap corruption BugLink: https://bugs.launchpad.net/bugs/2089340 [ Upstream commit 77b0b98bb743f5d04d8f995ba1936e1143689d4a ] In commit 75258f20fb70 ("btrfs: subpage: dump extra subpage bitmaps for debug") an internal macro GET_SUBPAGE_BITMAP() is introduced to grab the bitmap of each attribute. But that commit is using bitmap_cut() which will do the left shift of the larger bitmap, causing incorrect values. Thankfully this bitmap_cut() is only called for debug usage, and so far it's not yet causing problem. Fix it to use bitmap_read() to only grab the desired sub-bitmap. Fixes: 75258f20fb70 ("btrfs: subpage: dump extra subpage bitmaps for debug") CC: stable@vger.kernel.org # 6.6+ Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Sasha Levin Signed-off-by: Portia Stephens Signed-off-by: Stefan Bader --- fs/btrfs/subpage.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c index 0e49dab8dad2..fd2338630a24 100644 --- a/fs/btrfs/subpage.c +++ b/fs/btrfs/subpage.c @@ -725,8 +725,14 @@ void btrfs_folio_unlock_writer(struct btrfs_fs_info *fs_info, } #define GET_SUBPAGE_BITMAP(subpage, subpage_info, name, dst) \ - bitmap_cut(dst, subpage->bitmaps, 0, \ - subpage_info->name##_offset, subpage_info->bitmap_nr_bits) +{ \ + const int bitmap_nr_bits = subpage_info->bitmap_nr_bits; \ + \ + ASSERT(bitmap_nr_bits < BITS_PER_LONG); \ + *dst = bitmap_read(subpage->bitmaps, \ + subpage_info->name##_offset, \ + bitmap_nr_bits); \ +} void __cold btrfs_subpage_dump_bitmap(const struct btrfs_fs_info *fs_info, struct folio *folio, u64 start, u32 len)