A syzbot fault injection test reported that nilfs_btnode_create_block, a helper function that allocates a new node block for b-trees, causes a kernel BUG for disk images where the file system block size is smaller than the page size. This was due to unexpected flags on the newly allocated buffer head, and it turned out to be because the buffer flags were not cleared by nilfs_btnode_abort_change_key() after an error occurred during a b-tree update operation and the buffer was later reused in that state. Fix this issue by using nilfs_btnode_delete() to abandon the unused preallocated buffer in nilfs_btnode_abort_change_key(). Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> Reported-by: syzbot+b0a35a5c1f7e846d3b09@xxxxxxxxxxxxxxxxxxxxxxxxx Closes: https://lkml.kernel.org/r/000000000000d1d6c205ebc4d512@xxxxxxxxxx Tested-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx --- fs/nilfs2/btnode.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/fs/nilfs2/btnode.c b/fs/nilfs2/btnode.c index e956f886a1a1..5710833ac1cc 100644 --- a/fs/nilfs2/btnode.c +++ b/fs/nilfs2/btnode.c @@ -285,6 +285,14 @@ void nilfs_btnode_abort_change_key(struct address_space *btnc, if (nbh == NULL) { /* blocksize == pagesize */ xa_erase_irq(&btnc->i_pages, newkey); unlock_page(ctxt->bh->b_page); - } else - brelse(nbh); + } else { + /* + * When canceling a buffer that a prepare operation has + * allocated to copy a node block to another location, use + * nilfs_btnode_delete() to initialize and release the buffer + * so that the buffer flags will not be in an inconsistent + * state when it is reallocated. + */ + nilfs_btnode_delete(nbh); + } } -- 2.34.1
