| Message ID | 2bf30957-ad04-473a-a72e-8baab648fb56@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | pstore: Fix uaf when backend is unregistered | expand |
On Wed, Oct 09, 2024 at 01:10:14AM +0800, Zach Wade wrote: > when unload pstore_blk, we will unlink the pstore file and > set pos->dentry to NULL, but simple_unlink(d_inode(root), pos->dentry) > may free inode of pos->dentry and free pos by free_pstore_private, > this may trigger uaf. kasan report: Thanks for this! I need to double check what happening here a bit more closely, as maybe some ordering changed after a43e0fc5e913 ("pstore: inode: Only d_invalidate() is needed") > @@ -316,9 +316,10 @@ int pstore_put_backend_records(struct pstore_info *psi) > list_for_each_entry_safe(pos, tmp, &records_list, list) { > if (pos->record->psi == psi) { > list_del_init(&pos->list); > - d_invalidate(pos->dentry); > - simple_unlink(d_inode(root), pos->dentry); > + unlink_dentry = pos->dentry; > pos->dentry = NULL; > + d_invalidate(unlink_dentry); > + simple_unlink(d_inode(root), unlink_dentry); But on the face of it, this does solve the UAF. I'll double-check that this isn't a result of the mentioned commit. -Kees
On 2024/10/9 1:23, Kees Cook wrote: > On Wed, Oct 09, 2024 at 01:10:14AM +0800, Zach Wade wrote: >> when unload pstore_blk, we will unlink the pstore file and >> set pos->dentry to NULL, but simple_unlink(d_inode(root), pos->dentry) >> may free inode of pos->dentry and free pos by free_pstore_private, >> this may trigger uaf. kasan report: > > Thanks for this! I need to double check what happening here a bit more > closely, as maybe some ordering changed after a43e0fc5e913 ("pstore: > inode: Only d_invalidate() is needed") > >> @@ -316,9 +316,10 @@ int pstore_put_backend_records(struct pstore_info *psi) >> list_for_each_entry_safe(pos, tmp, &records_list, list) { >> if (pos->record->psi == psi) { >> list_del_init(&pos->list); >> - d_invalidate(pos->dentry); >> - simple_unlink(d_inode(root), pos->dentry); >> + unlink_dentry = pos->dentry; >> pos->dentry = NULL; >> + d_invalidate(unlink_dentry); >> + simple_unlink(d_inode(root), unlink_dentry); > > But on the face of it, this does solve the UAF. I'll double-check that > this isn't a result of the mentioned commit. Hi Cook, However, I think a more appropriate solution to the problem here is to check the reference count when uninstalling the mount point. At the same time, the test script is attached: #!/bin/bash modprobe pstore_blk blkdev=/dev/sda2 best_effort=on mount -t pstore pstore /sys/fs/pstore sleep 2 umount /sys/fs/pstore modprobe -r pstore_blk Thanks, Zach > > -Kees >
On 2024/10/9 21:36, Zach Wade wrote: > > > On 2024/10/9 1:23, Kees Cook wrote: >> On Wed, Oct 09, 2024 at 01:10:14AM +0800, Zach Wade wrote: >>> when unload pstore_blk, we will unlink the pstore file and >>> set pos->dentry to NULL, but simple_unlink(d_inode(root), pos->dentry) >>> may free inode of pos->dentry and free pos by free_pstore_private, >>> this may trigger uaf. kasan report: >> >> Thanks for this! I need to double check what happening here a bit more >> closely, as maybe some ordering changed after a43e0fc5e913 ("pstore: >> inode: Only d_invalidate() is needed") >> >>> @@ -316,9 +316,10 @@ int pstore_put_backend_records(struct >>> pstore_info *psi) >>> list_for_each_entry_safe(pos, tmp, &records_list, list) { >>> if (pos->record->psi == psi) { >>> list_del_init(&pos->list); >>> - d_invalidate(pos->dentry); >>> - simple_unlink(d_inode(root), pos->dentry); >>> + unlink_dentry = pos->dentry; >>> pos->dentry = NULL; >>> + d_invalidate(unlink_dentry); >>> + simple_unlink(d_inode(root), unlink_dentry); >> >> But on the face of it, this does solve the UAF. I'll double-check that >> this isn't a result of the mentioned commit. > > Hi Cook, > > However, I think a more appropriate solution to the problem here is to > check the reference count when uninstalling the mount point. > > At the same time, the test script is attached: > #!/bin/bash > modprobe pstore_blk > blkdev=/dev/sda2 > best_effort=on > mount -t pstore pstore /sys/fs/pstore > sleep 2 > umount /sys/fs/pstore > modprobe -r pstore_blk > > Thanks, > Zach > >> > >> -Kees >> > friendly ping. Hi Cook, How are you doing? I really hope we can solve this problem. Thanks, Zach
diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c index 56815799ce79..7561693e0f32 100644 --- a/fs/pstore/inode.c +++ b/fs/pstore/inode.c @@ -306,7 +306,7 @@ static struct dentry *psinfo_lock_root(void) int pstore_put_backend_records(struct pstore_info *psi) { struct pstore_private *pos, *tmp; - struct dentry *root; + struct dentry *root, *unlink_dentry; root = psinfo_lock_root(); if (!root) @@ -316,9 +316,10 @@ int pstore_put_backend_records(struct pstore_info *psi) list_for_each_entry_safe(pos, tmp, &records_list, list) { if (pos->record->psi == psi) { list_del_init(&pos->list); - d_invalidate(pos->dentry); - simple_unlink(d_inode(root), pos->dentry); + unlink_dentry = pos->dentry; pos->dentry = NULL; + d_invalidate(unlink_dentry); + simple_unlink(d_inode(root), unlink_dentry); } } }
when unload pstore_blk, we will unlink the pstore file and set pos->dentry to NULL, but simple_unlink(d_inode(root), pos->dentry) may free inode of pos->dentry and free pos by free_pstore_private, this may trigger uaf. kasan report: kernel: ================================================================== kernel: BUG: KASAN: slab-use-after-free in pstore_put_backend_records+0x3a4/0x480 kernel: Write of size 8 at addr ffff8883efbe0390 by task modprobe/4308 kernel: kernel: CPU: 1 PID: 4308 Comm: modprobe Kdump: loaded Not tainted 6.10.9-arch1-2 #2 5fd36c90225554e2cc88363729bd91e76130a89f kernel: Hardware name: ASUS System Product Name/TUF GAMING X670E-PLUS, BIOS 3024 08/02/2024 kernel: Call Trace: kernel: <TASK> kernel: dump_stack_lvl+0x5d/0x80 kernel: print_report+0x174/0x505 kernel: ? __pfx__raw_spin_lock_irqsave+0x10/0x10 kernel: ? pstore_put_backend_records+0x3a4/0x480 kernel: kasan_report+0xd0/0x150 kernel: ? pstore_put_backend_records+0x3a4/0x480 kernel: pstore_put_backend_records+0x3a4/0x480 kernel: ? srso_alias_return_thunk+0x5/0xfbef5 kernel: pstore_unregister+0x88/0x1b0 kernel: unregister_pstore_zone+0x2f/0xd0 [pstore_zone 35171c701a99c31efe207b7a718dc583e4a6503a] kernel: pstore_blk_exit+0x30/0x90 [pstore_blk 589d82101219208d8968e3adda9b96a2d42df635] kernel: __do_sys_delete_module+0x350/0x560 kernel: ? __pfx___do_sys_delete_module+0x10/0x10 kernel: ? srso_alias_return_thunk+0x5/0xfbef5 kernel: ? __memcg_slab_free_hook+0x28e/0x470 kernel: ? __pfx___audit_syscall_exit+0x10/0x10 kernel: do_syscall_64+0x82/0x190 kernel: ? srso_alias_return_thunk+0x5/0xfbef5 kernel: ? do_syscall_64+0x8e/0x190 kernel: ? seq_read_iter+0x62f/0x1220 kernel: ? __x64_sys_openat+0x300/0x380 kernel: ? srso_alias_return_thunk+0x5/0xfbef5 kernel: ? kasan_save_track+0x14/0x30 kernel: ? srso_alias_return_thunk+0x5/0xfbef5 kernel: ? srso_alias_return_thunk+0x5/0xfbef5 kernel: ? vfs_read+0x9a7/0xf00 kernel: ? srso_alias_return_thunk+0x5/0xfbef5 kernel: ? __audit_syscall_exit+0x38a/0x520 kernel: ? __pfx_vfs_read+0x10/0x10 kernel: ? __pfx___audit_syscall_exit+0x10/0x10 kernel: ? srso_alias_return_thunk+0x5/0xfbef5 kernel: ? __audit_syscall_exit+0x38a/0x520 kernel: ? srso_alias_return_thunk+0x5/0xfbef5 kernel: ? __pfx___audit_syscall_exit+0x10/0x10 kernel: ? srso_alias_return_thunk+0x5/0xfbef5 kernel: ? __x64_sys_read+0x162/0x250 kernel: ? __pfx___x64_sys_read+0x10/0x10 kernel: ? srso_alias_return_thunk+0x5/0xfbef5 kernel: ? syscall_exit_to_user_mode_prepare+0x148/0x170 kernel: ? srso_alias_return_thunk+0x5/0xfbef5 kernel: ? syscall_exit_to_user_mode+0x73/0x1f0 kernel: ? srso_alias_return_thunk+0x5/0xfbef5 kernel: ? do_syscall_64+0x8e/0x190 kernel: ? syscall_exit_to_user_mode+0x73/0x1f0 kernel: ? srso_alias_return_thunk+0x5/0xfbef5 kernel: ? srso_alias_return_thunk+0x5/0xfbef5 kernel: entry_SYSCALL_64_after_hwframe+0x76/0x7e kernel: RIP: 0033:0x741f9d72946b kernel: Code: 73 01 c3 48 8b 0d a5 c8 0c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa b8 b0 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 75 c8 0c 00 f7 d8 64 89 01 48 kernel: RSP: 002b:00007ffed7e621f8 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0 kernel: RAX: ffffffffffffffda RBX: 00006455e060ed30 RCX: 0000741f9d72946b kernel: RDX: 0000000000000000 RSI: 0000000000000800 RDI: 00006455e060ed98 kernel: RBP: 00007ffed7e62220 R08: 1999999999999999 R09: 0000000000000000 kernel: R10: 0000741f9d7a5fe0 R11: 0000000000000206 R12: 0000000000000000 kernel: R13: 00007ffed7e62250 R14: 0000000000000000 R15: 0000000000000000 kernel: </TASK> kernel: kernel: Allocated by task 3957: kernel: kasan_save_stack+0x30/0x50 kernel: kasan_save_track+0x14/0x30 kernel: __kasan_kmalloc+0xaa/0xb0 kernel: pstore_mkfile+0x47e/0xbe0 kernel: pstore_get_backend_records+0x560/0x920 kernel: pstore_get_records+0xec/0x180 kernel: pstore_register+0x1c3/0x5a0 kernel: register_pstore_zone.cold+0x298/0x3d1 [pstore_zone] kernel: pstore_blk_init+0x63c/0xff0 [pstore_blk] kernel: do_one_initcall+0xa4/0x380 kernel: do_init_module+0x28a/0x7c0 kernel: load_module+0x7b57/0xb020 kernel: init_module_from_file+0xdf/0x150 kernel: idempotent_init_module+0x23c/0x780 kernel: __x64_sys_finit_module+0xbe/0x130 kernel: do_syscall_64+0x82/0x190 kernel: entry_SYSCALL_64_after_hwframe+0x76/0x7e kernel: kernel: Freed by task 4308: kernel: kasan_save_stack+0x30/0x50 kernel: kasan_save_track+0x14/0x30 kernel: kasan_save_free_info+0x3b/0x60 kernel: __kasan_slab_free+0x12c/0x1b0 kernel: kfree+0x198/0x3b0 kernel: evict+0x33d/0xab0 kernel: __dentry_kill+0x17f/0x590 kernel: dput+0x2d9/0x810 kernel: simple_unlink+0xf4/0x140 kernel: pstore_put_backend_records+0x271/0x480 kernel: pstore_unregister+0x88/0x1b0 kernel: unregister_pstore_zone+0x2f/0xd0 [pstore_zone] kernel: pstore_blk_exit+0x30/0x90 [pstore_blk] kernel: __do_sys_delete_module+0x350/0x560 kernel: do_syscall_64+0x82/0x190 kernel: entry_SYSCALL_64_after_hwframe+0x76/0x7e kernel: kernel: The buggy address belongs to the object at ffff8883efbe0380 which belongs to the cache kmalloc-64 of size 64 kernel: The buggy address is located 16 bytes inside of freed 64-byte region [ffff8883efbe0380, ffff8883efbe03c0) kernel: kernel: The buggy address belongs to the physical page: kernel: page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3efbe0 kernel: memcg:ffff8883ef245801 kernel: flags: 0x2ffff8000000000(node=0|zone=2|lastcpupid=0x1ffff) kernel: page_type: 0xffffefff(slab) kernel: raw: 02ffff8000000000 ffff88810004c8c0 ffffea00043dcc40 dead000000000004 kernel: raw: 0000000000000000 0000000000200020 00000001ffffefff ffff8883ef245801 kernel: page dumped because: kasan: bad access detected kernel: kernel: Memory state around the buggy address: kernel: ffff8883efbe0280: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc kernel: ffff8883efbe0300: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc kernel: >ffff8883efbe0380: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc kernel: ^ kernel: ffff8883efbe0400: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc kernel: ffff8883efbe0480: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc kernel: ================================================================== kernel: Disabling lock debugging due to kernel taint kernel: pstore: Unregistered pstore_blk as persistent store backend kernel: ------------[ cut here ]------------ place the pos->dentry = NULL before simple_unlink(d_inode(root), pos->dentry) Fixes: 609e28bb139e ("pstore: Remove filesystem records when backend is unregistered") Signed-off-by: Li XingYang <lixingyang1@qq.com> Signed-off-by: Zach Wade <zachwade.k@gmail.com> --- fs/pstore/inode.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)