On Wed, Oct 26, 2022 at 09:55:19PM -0400, Sasha Levin wrote: > This is a note to let you know that I've just added the patch titled > > kernfs: fix use-after-free in __kernfs_remove > > to the 5.10-stable tree which can be found at: > http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary > > The filename of the patch is: > kernfs-fix-use-after-free-in-__kernfs_remove.patch > and it can be found in the queue-5.10 subdirectory. > > If you, or anyone else, feels it should not be added to the stable tree, > please let <stable@xxxxxxxxxxxxxxx> know about it. > > > > commit dcfe8c010accdad535bc505e4f6257168cf5c1f0 > Author: Christian A. Ehrhardt <lk@xxxxxxx> > Date: Tue Sep 13 14:17:23 2022 +0200 > > kernfs: fix use-after-free in __kernfs_remove > > [ Upstream commit 4abc99652812a2ddf932f137515d5c5a04723538 ] > > Syzkaller managed to trigger concurrent calls to > kernfs_remove_by_name_ns() for the same file resulting in > a KASAN detected use-after-free. The race occurs when the root > node is freed during kernfs_drain(). > > To prevent this acquire an additional reference for the root > of the tree that is removed before calling __kernfs_remove(). > > Found by syzkaller with the following reproducer (slab_nomerge is > required): > > syz_mount_image$ext4(0x0, &(0x7f0000000100)='./file0\x00', 0x100000, 0x0, 0x0, 0x0, 0x0) > r0 = openat(0xffffffffffffff9c, &(0x7f0000000080)='/proc/self/exe\x00', 0x0, 0x0) > close(r0) > pipe2(&(0x7f0000000140)={0xffffffffffffffff, <r1=>0xffffffffffffffff}, 0x800) > mount$9p_fd(0x0, &(0x7f0000000040)='./file0\x00', &(0x7f00000000c0), 0x408, &(0x7f0000000280)={'trans=fd,', {'rfdno', 0x3d, r0}, 0x2c, {'wfdno', 0x3d, r1}, 0x2c, {[{@cache_loose}, {@mmap}, {@loose}, {@loose}, {@mmap}], [{@mask={'mask', 0x3d, '^MAY_EXEC'}}, {@fsmagic={'fsmagic', 0x3d, 0x10001}}, {@dont_hash}]}}) > > Sample report: > > ================================================================== > BUG: KASAN: use-after-free in kernfs_type include/linux/kernfs.h:335 [inline] > BUG: KASAN: use-after-free in kernfs_leftmost_descendant fs/kernfs/dir.c:1261 [inline] > BUG: KASAN: use-after-free in __kernfs_remove.part.0+0x843/0x960 fs/kernfs/dir.c:1369 > Read of size 2 at addr ffff8880088807f0 by task syz-executor.2/857 > > CPU: 0 PID: 857 Comm: syz-executor.2 Not tainted 6.0.0-rc3-00363-g7726d4c3e60b #5 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0x6e/0x91 lib/dump_stack.c:106 > print_address_description mm/kasan/report.c:317 [inline] > print_report.cold+0x5e/0x5e5 mm/kasan/report.c:433 > kasan_report+0xa3/0x130 mm/kasan/report.c:495 > kernfs_type include/linux/kernfs.h:335 [inline] > kernfs_leftmost_descendant fs/kernfs/dir.c:1261 [inline] > __kernfs_remove.part.0+0x843/0x960 fs/kernfs/dir.c:1369 > __kernfs_remove fs/kernfs/dir.c:1356 [inline] > kernfs_remove_by_name_ns+0x108/0x190 fs/kernfs/dir.c:1589 > sysfs_slab_add+0x133/0x1e0 mm/slub.c:5943 > __kmem_cache_create+0x3e0/0x550 mm/slub.c:4899 > create_cache mm/slab_common.c:229 [inline] > kmem_cache_create_usercopy+0x167/0x2a0 mm/slab_common.c:335 > p9_client_create+0xd4d/0x1190 net/9p/client.c:993 > v9fs_session_init+0x1e6/0x13c0 fs/9p/v9fs.c:408 > v9fs_mount+0xb9/0xbd0 fs/9p/vfs_super.c:126 > legacy_get_tree+0xf1/0x200 fs/fs_context.c:610 > vfs_get_tree+0x85/0x2e0 fs/super.c:1530 > do_new_mount fs/namespace.c:3040 [inline] > path_mount+0x675/0x1d00 fs/namespace.c:3370 > do_mount fs/namespace.c:3383 [inline] > __do_sys_mount fs/namespace.c:3591 [inline] > __se_sys_mount fs/namespace.c:3568 [inline] > __x64_sys_mount+0x282/0x300 fs/namespace.c:3568 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x38/0x90 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > RIP: 0033:0x7f725f983aed > Code: 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007f725f0f7028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 > RAX: ffffffffffffffda RBX: 00007f725faa3f80 RCX: 00007f725f983aed > RDX: 00000000200000c0 RSI: 0000000020000040 RDI: 0000000000000000 > RBP: 00007f725f9f419c R08: 0000000020000280 R09: 0000000000000000 > R10: 0000000000000408 R11: 0000000000000246 R12: 0000000000000000 > R13: 0000000000000006 R14: 00007f725faa3f80 R15: 00007f725f0d7000 > </TASK> > > Allocated by task 855: > kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38 > kasan_set_track mm/kasan/common.c:45 [inline] > set_alloc_info mm/kasan/common.c:437 [inline] > __kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:470 > kasan_slab_alloc include/linux/kasan.h:224 [inline] > slab_post_alloc_hook mm/slab.h:727 [inline] > slab_alloc_node mm/slub.c:3243 [inline] > slab_alloc mm/slub.c:3251 [inline] > __kmem_cache_alloc_lru mm/slub.c:3258 [inline] > kmem_cache_alloc+0xbf/0x200 mm/slub.c:3268 > kmem_cache_zalloc include/linux/slab.h:723 [inline] > __kernfs_new_node+0xd4/0x680 fs/kernfs/dir.c:593 > kernfs_new_node fs/kernfs/dir.c:655 [inline] > kernfs_create_dir_ns+0x9c/0x220 fs/kernfs/dir.c:1010 > sysfs_create_dir_ns+0x127/0x290 fs/sysfs/dir.c:59 > create_dir lib/kobject.c:63 [inline] > kobject_add_internal+0x24a/0x8d0 lib/kobject.c:223 > kobject_add_varg lib/kobject.c:358 [inline] > kobject_init_and_add+0x101/0x160 lib/kobject.c:441 > sysfs_slab_add+0x156/0x1e0 mm/slub.c:5954 > __kmem_cache_create+0x3e0/0x550 mm/slub.c:4899 > create_cache mm/slab_common.c:229 [inline] > kmem_cache_create_usercopy+0x167/0x2a0 mm/slab_common.c:335 > p9_client_create+0xd4d/0x1190 net/9p/client.c:993 > v9fs_session_init+0x1e6/0x13c0 fs/9p/v9fs.c:408 > v9fs_mount+0xb9/0xbd0 fs/9p/vfs_super.c:126 > legacy_get_tree+0xf1/0x200 fs/fs_context.c:610 > vfs_get_tree+0x85/0x2e0 fs/super.c:1530 > do_new_mount fs/namespace.c:3040 [inline] > path_mount+0x675/0x1d00 fs/namespace.c:3370 > do_mount fs/namespace.c:3383 [inline] > __do_sys_mount fs/namespace.c:3591 [inline] > __se_sys_mount fs/namespace.c:3568 [inline] > __x64_sys_mount+0x282/0x300 fs/namespace.c:3568 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x38/0x90 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > Freed by task 857: > kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38 > kasan_set_track+0x21/0x30 mm/kasan/common.c:45 > kasan_set_free_info+0x20/0x40 mm/kasan/generic.c:370 > ____kasan_slab_free mm/kasan/common.c:367 [inline] > ____kasan_slab_free mm/kasan/common.c:329 [inline] > __kasan_slab_free+0x108/0x190 mm/kasan/common.c:375 > kasan_slab_free include/linux/kasan.h:200 [inline] > slab_free_hook mm/slub.c:1754 [inline] > slab_free_freelist_hook mm/slub.c:1780 [inline] > slab_free mm/slub.c:3534 [inline] > kmem_cache_free+0x9c/0x340 mm/slub.c:3551 > kernfs_put.part.0+0x2b2/0x520 fs/kernfs/dir.c:547 > kernfs_put+0x42/0x50 fs/kernfs/dir.c:521 > __kernfs_remove.part.0+0x72d/0x960 fs/kernfs/dir.c:1407 > __kernfs_remove fs/kernfs/dir.c:1356 [inline] > kernfs_remove_by_name_ns+0x108/0x190 fs/kernfs/dir.c:1589 > sysfs_slab_add+0x133/0x1e0 mm/slub.c:5943 > __kmem_cache_create+0x3e0/0x550 mm/slub.c:4899 > create_cache mm/slab_common.c:229 [inline] > kmem_cache_create_usercopy+0x167/0x2a0 mm/slab_common.c:335 > p9_client_create+0xd4d/0x1190 net/9p/client.c:993 > v9fs_session_init+0x1e6/0x13c0 fs/9p/v9fs.c:408 > v9fs_mount+0xb9/0xbd0 fs/9p/vfs_super.c:126 > legacy_get_tree+0xf1/0x200 fs/fs_context.c:610 > vfs_get_tree+0x85/0x2e0 fs/super.c:1530 > do_new_mount fs/namespace.c:3040 [inline] > path_mount+0x675/0x1d00 fs/namespace.c:3370 > do_mount fs/namespace.c:3383 [inline] > __do_sys_mount fs/namespace.c:3591 [inline] > __se_sys_mount fs/namespace.c:3568 [inline] > __x64_sys_mount+0x282/0x300 fs/namespace.c:3568 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x38/0x90 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > The buggy address belongs to the object at ffff888008880780 > which belongs to the cache kernfs_node_cache of size 128 > The buggy address is located 112 bytes inside of > 128-byte region [ffff888008880780, ffff888008880800) > > The buggy address belongs to the physical page: > page:00000000732833f8 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x8880 > flags: 0x100000000000200(slab|node=0|zone=1) > raw: 0100000000000200 0000000000000000 dead000000000122 ffff888001147280 > raw: 0000000000000000 0000000000150015 00000001ffffffff 0000000000000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: > ffff888008880680: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb > ffff888008880700: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc > >ffff888008880780: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ^ > ffff888008880800: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb > ffff888008880880: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc > ================================================================== > > Acked-by: Tejun Heo <tj@xxxxxxxxxx> > Cc: stable <stable@xxxxxxxxxx> # -rc3 It is not -rc3 yet, so I'll go drop this and wait until then :( thanks, greg k-h
