Wind River Support Network

Description

In the Linux kernel, the following vulnerability has been resolved:  f2fs: fix UAF caused by decrementing sbi->nr_pages[] in f2fs_write_end_io()  The xfstests case "generic/107" and syzbot have both reported a NULL pointer dereference.  The concurrent scenario that triggers the panic is as follows:  F2FS_WB_CP_DATA write callback          umount                                         - f2fs_write_checkpoint                                          - f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA) - blk_mq_end_request  - bio_endio   - f2fs_write_end_io    : dec_page_count(sbi, F2FS_WB_CP_DATA)    : wake_up(&sbi->cp_wait)                                         - kill_f2fs_super                                          - kill_block_super                                           - f2fs_put_super                                            : iput(sbi->node_inode)                                            : sbi->node_inode = NULL    : f2fs_in_warm_node_list     - is_node_folio // sbi->node_inode is NULL and panic  The root cause is that f2fs_put_super() calls iput(sbi->node_inode) and sets sbi->node_inode to NULL after sbi->nr_pages[F2FS_WB_CP_DATA] is decremented to zero. As a result, f2fs_in_warm_node_list() may dereference a NULL node_inode when checking whether a folio belongs to the node inode, leading to a panic.  This patch fixes the issue by calling f2fs_in_warm_node_list() before decrementing sbi->nr_pages[F2FS_WB_CP_DATA], thus preventing the use-after-free condition.