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* rqst[1,2,3] is allocated in vars * each rqst->rq_iov is also allocated in vars or using pooled memory SMB2_open_free, SMB2_ioctl_free, SMB2_query_info_free are iterating on each rqst after vars has been freed (use-after-free), and they are freeing the kvec a second time (double-free). How to trigger: * compile with KASAN * mount a share $ smbinfo quota /mnt/foo Segmentation fault $ dmesg ================================================================== BUG: KASAN: use-after-free in SMB2_open_free+0x1c/0xa0 Read of size 8 at addr ffff888007b10c00 by task python3/1200 CPU: 2 PID: 1200 Comm: python3 Not tainted 5.12.0-rc6+ #107 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.14.0-0-g155821a-rebuilt.opensuse.org 04/01/2014 Call Trace: dump_stack+0x93/0xc2 print_address_description.constprop.0+0x18/0x130 ? SMB2_open_free+0x1c/0xa0 ? SMB2_open_free+0x1c/0xa0 kasan_report.cold+0x7f/0x111 ? smb2_ioctl_query_info+0x240/0x990 ? SMB2_open_free+0x1c/0xa0 SMB2_open_free+0x1c/0xa0 smb2_ioctl_query_info+0x2bf/0x990 ? smb2_query_reparse_tag+0x600/0x600 ? cifs_mapchar+0x250/0x250 ? rcu_read_lock_sched_held+0x3f/0x70 ? cifs_strndup_to_utf16+0x12c/0x1c0 ? rwlock_bug.part.0+0x60/0x60 ? rcu_read_lock_sched_held+0x3f/0x70 ? cifs_convert_path_to_utf16+0xf8/0x140 ? smb2_check_message+0x6f0/0x6f0 cifs_ioctl+0xf18/0x16b0 ? smb2_query_reparse_tag+0x600/0x600 ? cifs_readdir+0x1800/0x1800 ? selinux_bprm_creds_for_exec+0x4d0/0x4d0 ? do_user_addr_fault+0x30b/0x950 ? __x64_sys_openat+0xce/0x140 __x64_sys_ioctl+0xb9/0xf0 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7fdcf1f4ba87 Code: b3 66 90 48 8b 05 11 14 2c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d e1 13 2c 00 f7 d8 64 89 01 48 RSP: 002b:00007ffef1ce7748 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000c018cf07 RCX: 00007fdcf1f4ba87 RDX: 0000564c467c5590 RSI: 00000000c018cf07 RDI: 0000000000000003 RBP: 00007ffef1ce7770 R08: 00007ffef1ce7420 R09: 00007fdcf0e0562b R10: 0000000000000100 R11: 0000000000000246 R12: 0000000000004018 R13: 0000000000000001 R14: 0000000000000003 R15: 0000564c467c5590 Allocated by task 1200: kasan_save_stack+0x1b/0x40 __kasan_kmalloc+0x7a/0x90 smb2_ioctl_query_info+0x10e/0x990 cifs_ioctl+0xf18/0x16b0 __x64_sys_ioctl+0xb9/0xf0 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xae Freed by task 1200: kasan_save_stack+0x1b/0x40 kasan_set_track+0x1c/0x30 kasan_set_free_info+0x20/0x30 __kasan_slab_free+0xe5/0x110 slab_free_freelist_hook+0x53/0x130 kfree+0xcc/0x320 smb2_ioctl_query_info+0x2ad/0x990 cifs_ioctl+0xf18/0x16b0 __x64_sys_ioctl+0xb9/0xf0 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xae The buggy address belongs to the object at ffff888007b10c00 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 0 bytes inside of 512-byte region [ffff888007b10c00, ffff888007b10e00) The buggy address belongs to the page: page:0000000044e14b75 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7b10 head:0000000044e14b75 order:2 compound_mapcount:0 compound_pincount:0 flags: 0x100000000010200(slab|head) raw: 0100000000010200 ffffea000015f500 0000000400000004 ffff888001042c80 raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888007b10b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888007b10b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff888007b10c00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888007b10c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888007b10d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== Signed-off-by: Aurelien Aptel <aaptel@suse.com> CC: <stable@vger.kernel.org> Signed-off-by: Steve French <stfrench@microsoft.com>
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.