CVE-2024-46687: In the Linux kernel, the following vulnerability has been resolved:  btrfs: fix a use-after-free when hitting errors inside btrfs_submit_chunk()  [BUG] There is an internal report that KASAN is reporting use-after-free, with the following backtrace:    BUG: KASAN: slab-use-after-free in btrfs_check_read_bio+0xa68/0xb70 [btrfs]   Read of size 4 at addr ffff8881117cec28 by task kworker/u16:2/45   CPU: 1 UID: 0 PID: 45 Comm: kworker/u16:2 Not tainted 6.11.0-rc2-next-20240805-default+ #76   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-3-gd478f380-rebuilt.opensuse.org 04/01/2014   Workqueue: btrfs-endio btrfs_end_bio_work [btrfs]   Call Trace:    dump_stack_lvl+0x61/0x80    print_address_description.constprop.0+0x5e/0x2f0    print_report+0x118/0x216    kasan_report+0x11d/0x1f0    btrfs_check_read_bio+0xa68/0xb70 [btrfs]    process_one_work+0xce0/0x12a0    worker_thread+0x717/0x1250    kthread+0x2e3/0x3c0    ret_from_fork+0x2d/0x70    ret_from_fork_asm+0x11/0x20    Allocated by task 20917:    kasan_save_stack+0x37/0x60    kasan_save_track+0x10/0x30    __kasan_slab_alloc+0x7d/0x80    kmem_cache_alloc_noprof+0x16e/0x3e0    mempool_alloc_noprof+0x12e/0x310    bio_alloc_bioset+0x3f0/0x7a0    btrfs_bio_alloc+0x2e/0x50 [btrfs]    submit_extent_page+0x4d1/0xdb0 [btrfs]    btrfs_do_readpage+0x8b4/0x12a0 [btrfs]    btrfs_readahead+0x29a/0x430 [btrfs]    read_pages+0x1a7/0xc60    page_cache_ra_unbounded+0x2ad/0x560    filemap_get_pages+0x629/0xa20    filemap_read+0x335/0xbf0    vfs_read+0x790/0xcb0    ksys_read+0xfd/0x1d0    do_syscall_64+0x6d/0x140    entry_SYSCALL_64_after_hwframe+0x4b/0x53    Freed by task 20917:    kasan_save_stack+0x37/0x60    kasan_save_track+0x10/0x30    kasan_save_free_info+0x37/0x50    __kasan_slab_free+0x4b/0x60    kmem_cache_free+0x214/0x5d0    bio_free+0xed/0x180    end_bbio_data_read+0x1cc/0x580 [btrfs]    btrfs_submit_chunk+0x98d/0x1880 [btrfs]    btrfs_submit_bio+0x33/0x70 [btrfs]    submit_one_bio+0xd4/0x130 [btrfs]    submit_extent_page+0x3ea/0xdb0 [btrfs]    btrfs_do_readpage+0x8b4/0x12a0 [btrfs]    btrfs_readahead+0x29a/0x430 [btrfs]    read_pages+0x1a7/0xc60    page_cache_ra_unbounded+0x2ad/0x560    filemap_get_pages+0x629/0xa20    filemap_read+0x335/0xbf0    vfs_read+0x790/0xcb0    ksys_read+0xfd/0x1d0    do_syscall_64+0x6d/0x140    entry_SYSCALL_64_after_hwframe+0x4b/0x53  [CAUSE] Although I cannot reproduce the error, the report itself is good enough to pin down the cause.  The call trace is the regular endio workqueue context, but the free-by-task trace is showing that during btrfs_submit_chunk() we already hit a critical error, and is calling btrfs_bio_end_io() to error out.  And the original endio function called bio_put() to free the whole bio.  This means a double freeing thus causing use-after-free, e.g.:  1. Enter btrfs_submit_bio() with a read bio    The read bio length is 128K, crossing two 64K stripes.  2. The first run of btrfs_submit_chunk()  2.1 Call btrfs_map_block(), which returns 64K 2.2 Call btrfs_split_bio()     Now there are two bios, one referring to the first 64K, the other     referring to the second 64K. 2.3 The first half is submitted.  3. The second run of btrfs_submit_chunk()  3.1 Call btrfs_map_block(), which by somehow failed     Now we call btrfs_bio_end_io() to handle the error  3.2 btrfs_bio_end_io() calls the original endio function     Which is end_bbio_data_read(), and it calls bio_put() for the     original bio.      Now the original bio is freed.  4. The submitted first 64K bio finished    Now we call into btrfs_check_read_bio() and tries to advance the bio    iter.    But since the original bio (thus its iter) is already freed, we    trigger the above use-after free.     And even if the memory is not poisoned/corrupted, we will later call    the original endio function, causing a double freeing.  [FIX] Instead of calling btrfs_bio_end_io(), call btrfs_orig_bbio_end_io(), which has the extra check on split bios and do the pr ---truncated---