From: Brian Foster Date: Fri, 16 May 2025 17:38:00 +0000 (-0400) Subject: ext4: only dirty folios when data journaling regular files X-Git-Tag: v6.16-rc1~139^2~5 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e26268ff1dcae5662c1b96c35f18cfa6ab73d9de;p=thirdparty%2Flinux.git ext4: only dirty folios when data journaling regular files fstest generic/388 occasionally reproduces a crash that looks as follows: BUG: kernel NULL pointer dereference, address: 0000000000000000 ... Call Trace: ext4_block_zero_page_range+0x30c/0x380 [ext4] ext4_truncate+0x436/0x440 [ext4] ext4_process_orphan+0x5d/0x110 [ext4] ext4_orphan_cleanup+0x124/0x4f0 [ext4] ext4_fill_super+0x262d/0x3110 [ext4] get_tree_bdev_flags+0x132/0x1d0 vfs_get_tree+0x26/0xd0 vfs_cmd_create+0x59/0xe0 __do_sys_fsconfig+0x4ed/0x6b0 do_syscall_64+0x82/0x170 ... This occurs when processing a symlink inode from the orphan list. The partial block zeroing code in the truncate path calls ext4_dirty_journalled_data() -> folio_mark_dirty(). The latter calls mapping->a_ops->dirty_folio(), but symlink inodes are not assigned an a_ops vector in ext4, hence the crash. To avoid this problem, update the ext4_dirty_journalled_data() helper to only mark the folio dirty on regular files (for which a_ops is assigned). This also matches the journaling logic in the ext4_symlink() creation path, where ext4_handle_dirty_metadata() is called directly. Fixes: d84c9ebdac1e ("ext4: Mark pages with journalled data dirty") Signed-off-by: Brian Foster Link: https://patch.msgid.link/20250516173800.175577-1-bfoster@redhat.com Signed-off-by: Theodore Ts'o Reviewed-by: Jan Kara Cc: stable@kernel.org --- diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 2f59036df8009..ce0632094c50c 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -1119,7 +1119,12 @@ int ext4_walk_page_buffers(handle_t *handle, struct inode *inode, */ static int ext4_dirty_journalled_data(handle_t *handle, struct buffer_head *bh) { - folio_mark_dirty(bh->b_folio); + struct folio *folio = bh->b_folio; + struct inode *inode = folio->mapping->host; + + /* only regular files have a_ops */ + if (S_ISREG(inode->i_mode)) + folio_mark_dirty(folio); return ext4_handle_dirty_metadata(handle, NULL, bh); }