On Thu, Jul 07, 2022 at 04:09:29AM +0100, Matthew Wilcox wrote:
> On Thu, Jul 07, 2022 at 10:09:38AM +0800, Liu Shixin wrote:
> > Release refcount after xas_set to fix UAF which may cause panic like this:
> >
> > page:ffffea000491fa40 refcount:1 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x1247e9
> > head:ffffea000491fa00 order:3 compound_mapcount:0 compound_pincount:0
> > memcg:ffff888104f91091
> > flags: 0x2fffff80010200(slab|head|node=0|zone=2|lastcpupid=0x1fffff)
> > ...
> > page dumped because: VM_BUG_ON_PAGE(PageTail(page))
> > ------------[ cut here ]------------
> > kernel BUG at include/linux/page-flags.h:632!
> > invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN
> > CPU: 1 PID: 7642 Comm: sh Not tainted 5.15.51-dirty #26
> > ...
> > Call Trace:
> > <TASK>
> > __invalidate_mapping_pages+0xe7/0x540
> > drop_pagecache_sb+0x159/0x320
> > iterate_supers+0x120/0x240
> > drop_caches_sysctl_handler+0xaa/0xe0
> > proc_sys_call_handler+0x2b4/0x480
> > new_sync_write+0x3d6/0x5c0
> > vfs_write+0x446/0x7a0
> > ksys_write+0x105/0x210
> > do_syscall_64+0x35/0x80
> > entry_SYSCALL_64_after_hwframe+0x44/0xae
> > RIP: 0033:0x7f52b5733130
> > ...
> >
> > This problem has been fixed on mainline by patch 6b24ca4a1a8d ("mm: Use
> > multi-index entries in the page cache") since it deletes the related code.
> >
> > Fixes: 5c211ba29deb ("mm: add and use find_lock_entries")
> > Signed-off-by: Liu Shixin <liushixin2@xxxxxxxxxx>
>
> Acked-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Now queued up, thanks.
greg k-h
