In the Linux kernel, the following vulnerability has been resolved:
nfsd: return -EINVAL when namelen is 0
When we have a corrupted main.sqlite in /var/lib/nfs/nfsdcld/, it may result in namelen being 0, which will cause memdupuser() to return ZEROSIZEPTR. When we access the name.data that has been assigned the value of ZEROSIZEPTR in nfs4clienttoreclaim(), null pointer dereference is triggered.
[ T1205] ================================================================== [ T1205] BUG: KASAN: null-ptr-deref in nfs4clienttoreclaim+0xe9/0x260 [ T1205] Read of size 1 at addr 0000000000000010 by task nfsdcld/1205 [ T1205] [ T1205] CPU: 11 PID: 1205 Comm: nfsdcld Not tainted 5.10.0-00003-g2c1423731b8d #406 [ T1205] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 04/01/2014 [ T1205] Call Trace: [ T1205] dumpstack+0x9a/0xd0 [ T1205] ? nfs4clienttoreclaim+0xe9/0x260 [ T1205] _kasanreport.cold+0x34/0x84 [ T1205] ? nfs4clienttoreclaim+0xe9/0x260 [ T1205] kasanreport+0x3a/0x50 [ T1205] nfs4clienttoreclaim+0xe9/0x260 [ T1205] ? nfsd4releaselockowner+0x410/0x410 [ T1205] cldpipedowncall+0x5ca/0x760 [ T1205] ? nfsd4cldtrackingexit+0x1d0/0x1d0 [ T1205] ? downwritekillablenested+0x170/0x170 [ T1205] ? avcpolicyseqno+0x28/0x40 [ T1205] ? selinuxfilepermission+0x1b4/0x1e0 [ T1205] rpcpipewrite+0x84/0xb0 [ T1205] vfswrite+0x143/0x520 [ T1205] ksyswrite+0xc9/0x170 [ T1205] ? _ia32sysread+0x50/0x50 [ T1205] ? ktimegetcoarserealts64+0xfe/0x110 [ T1205] ? ktimegetcoarserealts64+0xa2/0x110 [ T1205] dosyscall64+0x33/0x40 [ T1205] entrySYSCALL64afterhwframe+0x67/0xd1 [ T1205] RIP: 0033:0x7fdbdb761bc7 [ T1205] Code: 0f 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 514 [ T1205] RSP: 002b:00007fff8c4b7248 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 [ T1205] RAX: ffffffffffffffda RBX: 000000000000042b RCX: 00007fdbdb761bc7 [ T1205] RDX: 000000000000042b RSI: 00007fff8c4b75f0 RDI: 0000000000000008 [ T1205] RBP: 00007fdbdb761bb0 R08: 0000000000000000 R09: 0000000000000001 [ T1205] R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000042b [ T1205] R13: 0000000000000008 R14: 00007fff8c4b75f0 R15: 0000000000000000 [ T1205] ==================================================================
Fix it by checking namelen.