066a5b6784
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@huawei.com> Acked-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.