DEBIAN-CVE-2021-46955

In the Linux kernel, the following vulnerability has been resolved: openvswitch: fix stack OOB read while fragmenting IPv4 packets running openvswitch on kernels built with KASAN, it's possible to see the following splat while testing fragmentation of IPv4 packets: BUG: KASAN: stack-out-of-bounds in ipdofragment+0x1b03/0x1f60 Read of size 1 at addr ffff888112fc713c by task handler2/1367 CPU: 0 PID: 1367 Comm: handler2 Not tainted 5.12.0-rc6+ #418 Hardware name: Red Hat KVM, BIOS 1.11.1-4.module+el8.1.0+4066+0f1aadab 04/01/2014 Call Trace: dumpstack+0x92/0xc1 printaddressdescription.constprop.7+0x1a/0x150 kasanreport.cold.13+0x7f/0x111 ipdofragment+0x1b03/0x1f60 ovsfragment+0x5bf/0x840 [openvswitch] doexecuteactions+0x1bd5/0x2400 [openvswitch] ovsexecuteactions+0xc8/0x3d0 [openvswitch] ovspacketcmdexecute+0xa39/0x1150 [openvswitch] genlfamilyrcvmsgdoit.isra.15+0x227/0x2d0 genlrcvmsg+0x287/0x490 netlinkrcvskb+0x120/0x380 genlrcv+0x24/0x40 netlinkunicast+0x439/0x630 netlinksendmsg+0x719/0xbf0 socksendmsg+0xe2/0x110 _syssendmsg+0x5ba/0x890 syssendmsg+0xe9/0x160 _syssendmsg+0xd3/0x170 dosyscall64+0x33/0x40 entrySYSCALL64afterhwframe+0x44/0xae RIP: 0033:0x7f957079db07 Code: c3 66 90 41 54 41 89 d4 55 48 89 f5 53 89 fb 48 83 ec 10 e8 eb ec ff ff 44 89 e2 48 89 ee 89 df 41 89 c0 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 44 89 c7 48 89 44 24 08 e8 24 ed ff ff 48 RSP: 002b:00007f956ce35a50 EFLAGS: 00000293 ORIGRAX: 000000000000002e RAX: ffffffffffffffda RBX: 0000000000000019 RCX: 00007f957079db07 RDX: 0000000000000000 RSI: 00007f956ce35ae0 RDI: 0000000000000019 RBP: 00007f956ce35ae0 R08: 0000000000000000 R09: 00007f9558006730 R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000 R13: 00007f956ce37308 R14: 00007f956ce35f80 R15: 00007f956ce35ae0 The buggy address belongs to the page: page:00000000af2a1d93 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x112fc7 flags: 0x17ffffc0000000() raw: 0017ffffc0000000 0000000000000000 dead000000000122 0000000000000000 raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: kasan: bad access detected addr ffff888112fc713c is located in stack of task handler2/1367 at offset 180 in frame: ovsfragment+0x0/0x840 [openvswitch] this frame has 2 objects: [32, 144) 'ovsdst' [192, 424) 'ovsrt' Memory state around the buggy address: ffff888112fc7000: f3 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff888112fc7080: 00 f1 f1 f1 f1 00 00 00 00 00 00 00 00 00 00 00 >ffff888112fc7100: 00 00 00 f2 f2 f2 f2 f2 f2 00 00 00 00 00 00 00 ^ ffff888112fc7180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff888112fc7200: 00 00 00 00 00 00 f2 f2 f2 00 00 00 00 00 00 00 for IPv4 packets, ovsfragment() uses a temporary struct dstentry. Then, in the following call graph: ipdofragment() ipskbdstmtu() ipdstmtumaybeforward() ipmtulocked() the pointer to struct dstentry is used as pointer to struct rtable: this turns the access to struct members like rtmtulocked into an OOB read in the stack. Fix this changing the temporary variable used for IPv4 packets in ovs_fragment(), similarly to what is done for IPv6 few lines below.