Fri, 25 Sep 2020 01:57:16 -0700 > syzbot found the following issue on: > > HEAD commit: 171d4ff7 Merge tag 'mmc-v5.9-rc4-2' of git://git.kernel.or.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=17d457b5900000 > kernel config: https://syzkaller.appspot.com/x/.config?x=5f4c828c9e3cef97 > dashboard link: https://syzkaller.appspot.com/bug?extid=2d0585e5efcd43d113c2 > compiler: gcc (GCC) 10.1.0-syz 20200507 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16a33ad3900000 > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+2d0585e5efcd43d113c2@xxxxxxxxxxxxxxxxxxxxxxxxx > > ================================================================== > BUG: KASAN: use-after-free in memcpy include/linux/string.h:406 [inline] > BUG: KASAN: use-after-free in fscache_set_key fs/fscache/cookie.c:93 [inline] > BUG: KASAN: use-after-free in fscache_alloc_cookie+0xff/0x730 fs/fscache/cookie.c:153 > Read of size 10 at addr ffff8880a6c28200 by task kworker/1:6/8760 > > CPU: 1 PID: 8760 Comm: kworker/1:6 Not tainted 5.9.0-rc6-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > Workqueue: afs afs_manage_cell > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0x198/0x1fd lib/dump_stack.c:118 > print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383 > __kasan_report mm/kasan/report.c:513 [inline] > kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530 > check_memory_region_inline mm/kasan/generic.c:186 [inline] > check_memory_region+0x13d/0x180 mm/kasan/generic.c:192 > memcpy+0x20/0x60 mm/kasan/common.c:105 > memcpy include/linux/string.h:406 [inline] > fscache_set_key fs/fscache/cookie.c:93 [inline] > fscache_alloc_cookie+0xff/0x730 fs/fscache/cookie.c:153 > __fscache_acquire_cookie+0x16c/0x610 fs/fscache/cookie.c:288 > fscache_acquire_cookie include/linux/fscache.h:334 [inline] > afs_activate_cell fs/afs/cell.c:609 [inline] > afs_manage_cell+0x4fa/0x11c0 fs/afs/cell.c:697 > process_one_work+0x94c/0x1670 kernel/workqueue.c:2269 > worker_thread+0x64c/0x1120 kernel/workqueue.c:2415 > kthread+0x3b5/0x4a0 kernel/kthread.c:292 > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 > > Allocated by task 10197: > kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48 > kasan_set_track mm/kasan/common.c:56 [inline] > __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461 > __do_kmalloc mm/slab.c:3655 [inline] > __kmalloc+0x1b0/0x360 mm/slab.c:3664 > kmalloc include/linux/slab.h:559 [inline] > afs_alloc_cell fs/afs/cell.c:157 [inline] > afs_lookup_cell+0x5e9/0x1440 fs/afs/cell.c:262 > afs_parse_source fs/afs/super.c:290 [inline] > afs_parse_param+0x404/0x8c0 fs/afs/super.c:326 > vfs_parse_fs_param fs/fs_context.c:117 [inline] > vfs_parse_fs_param+0x203/0x550 fs/fs_context.c:98 > vfs_parse_fs_string+0xe6/0x150 fs/fs_context.c:161 > generic_parse_monolithic+0x16f/0x1f0 fs/fs_context.c:201 > do_new_mount fs/namespace.c:2871 [inline] > path_mount+0x133f/0x20a0 fs/namespace.c:3192 > do_mount fs/namespace.c:3205 [inline] > __do_sys_mount fs/namespace.c:3413 [inline] > __se_sys_mount fs/namespace.c:3390 [inline] > __x64_sys_mount+0x27f/0x300 fs/namespace.c:3390 > do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 > entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > Freed by task 16: > kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48 > kasan_set_track+0x1c/0x30 mm/kasan/common.c:56 > kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355 > __kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422 > __cache_free mm/slab.c:3418 [inline] > kfree+0x10e/0x2b0 mm/slab.c:3756 > afs_cell_destroy+0x1b0/0x240 fs/afs/cell.c:500 > rcu_do_batch kernel/rcu/tree.c:2428 [inline] > rcu_core+0x5ca/0x1130 kernel/rcu/tree.c:2656 > __do_softirq+0x1f8/0xb23 kernel/softirq.c:298 > > The buggy address belongs to the object at ffff8880a6c28200 > which belongs to the cache kmalloc-32 of size 32 > The buggy address is located 0 bytes inside of > 32-byte region [ffff8880a6c28200, ffff8880a6c28220) > The buggy address belongs to the page: > page:00000000c2f50dc7 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8880a6c28fc1 pfn:0xa6c28 > flags: 0xfffe0000000200(slab) > raw: 00fffe0000000200 ffffea00028969c8 ffffea00025ca748 ffff8880aa040100 > raw: ffff8880a6c28fc1 ffff8880a6c28000 000000010000003f 0000000000000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: > ffff8880a6c28100: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc > ffff8880a6c28180: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc > >ffff8880a6c28200: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc > ^ > ffff8880a6c28280: 00 00 00 00 fc fc fc fc 00 fc fc fc fc fc fc fc > ffff8880a6c28300: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc > ================================================================== Flush the manager work before releasing cell's resources to avoid uaf. To that end, add the AFS_CELL_DESTROYING cell state to infom the kworker that there's no more job to do. --- a/fs/afs/internal.h +++ b/fs/afs/internal.h @@ -344,6 +344,7 @@ enum afs_cell_state { AFS_CELL_DEACTIVATING, AFS_CELL_INACTIVE, AFS_CELL_FAILED, + AFS_CELL_DESTROYING, }; /* --- a/fs/afs/cell.c +++ b/fs/afs/cell.c @@ -493,6 +493,7 @@ static void afs_cell_destroy(struct rcu_ ASSERTCMP(atomic_read(&cell->usage), ==, 0); + flush_work(&cell->manager); afs_put_volume(cell->net, cell->root_volume, afs_volume_trace_put_cell_root); afs_put_vlserverlist(cell->net, rcu_access_pointer(cell->vl_servers)); afs_put_cell(cell->net, cell->alias_of); @@ -672,13 +673,17 @@ static void afs_manage_cell(struct work_ again: _debug("state %u", cell->state); switch (cell->state) { + case AFS_CELL_DESTROYING: + return; case AFS_CELL_INACTIVE: case AFS_CELL_FAILED: write_seqlock(&net->cells_lock); usage = 1; deleted = atomic_try_cmpxchg_relaxed(&cell->usage, &usage, 0); - if (deleted) + if (deleted) { rb_erase(&cell->net_node, &net->cells); + cell->state = AFS_CELL_DESTROYING; + } write_sequnlock(&net->cells_lock); if (deleted) goto final_destruction; -- Linux-cachefs mailing list Linux-cachefs@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cachefs
