commit 782e53d0c14420858dbf0f8f797973c150d3b6d7 upstream. In a syzbot stress test that deliberately causes file system errors on nilfs2 with a corrupted disk image, it has been reported that nilfs_clear_dirty_page() called from nilfs_clear_dirty_pages() can cause a general protection fault. In nilfs_clear_dirty_pages(), when looking up dirty pages from the page cache and calling nilfs_clear_dirty_page() for each dirty page/folio retrieved, the back reference from the argument page to "mapping" may have been changed to NULL (and possibly others). It is necessary to check this after locking the page/folio. So, fix this issue by not calling nilfs_clear_dirty_page() on a page/folio after locking it in nilfs_clear_dirty_pages() if the back reference "mapping" from the page/folio is different from the "mapping" that held the page/folio just before. Link: https://lkml.kernel.org/r/20230612021456.3682-1-konishi.ryusuke@xxxxxxxxx Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> Reported-by: syzbot+53369d11851d8f26735c@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://lkml.kernel.org/r/000000000000da4f6b05eb9bf593@xxxxxxxxxx Tested-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> --- Please apply this patch to the above stable trees instead of the patch that could not be applied to them. This patch resolves the conflict caused by the recent page to folio conversion applied in nilfs_clear_dirty_pages(). The general protection fault reported by syzbot reproduces on these stable kernels before the page/folio conversion is applied. This fixes it. With this tweak, this patch is applicable from v3.10 to v6.2. Also, this patch has been tested against the -stable trees of each version in the subject prefix. fs/nilfs2/page.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/fs/nilfs2/page.c b/fs/nilfs2/page.c index 39b7eea2642a..7d31833e68d1 100644 --- a/fs/nilfs2/page.c +++ b/fs/nilfs2/page.c @@ -369,7 +369,15 @@ void nilfs_clear_dirty_pages(struct address_space *mapping, bool silent) struct page *page = pvec.pages[i]; lock_page(page); - nilfs_clear_dirty_page(page, silent); + + /* + * This page may have been removed from the address + * space by truncation or invalidation when the lock + * was acquired. Skip processing in that case. + */ + if (likely(page->mapping == mapping)) + nilfs_clear_dirty_page(page, silent); + unlock_page(page); } pagevec_release(&pvec); -- 2.39.3
