Date: Thu, 25 Nov 2021 12:10:04 +0000 From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 260046] An NFS v4 client can crash the server with a LISTXATTRS RPC Message-ID: <bug-260046-227@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D260046 Bug ID: 260046 Summary: An NFS v4 client can crash the server with a LISTXATTRS RPC Product: Base System Version: CURRENT Hardware: Any OS: Any Status: New Severity: Affects Some People Priority: --- Component: kern Assignee: bugs@FreeBSD.org Reporter: rtm@lcs.mit.edu Attachment #229724 text/plain mime type: Created attachment 229724 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=3D229724&action= =3Dedit Demo of an NFS client crashing a server with LISTXATTRS. nfsrvd_listxattr() calls nfsvno_listxattr(). The latter can return zero at the same time as leaving buf =3D=3D NULL. But if the return value is zero, nfsrvd_listxattr() dereferences the NULL buf, causing a crash. I've attached a demo: # uname -a FreeBSD 14.0-CURRENT FreeBSD 14.0-CURRENT #99 main-n250901-77e3db078984-di= rty: Wed Nov 24 05:42:01 EST 2021=20=20=20=20 rtm@xxx:/usr/obj/usr/rtm/symbsd/src/riscv.riscv64/sys/RTM riscv # cc fnfsd_3.c # ./a.out ... panic: Fatal page fault at 0xffffffc00026f256: 0000000000000000 cpuid =3D 0 time =3D 1637841164 KDB: stack backtrace: db_trace_self() at db_trace_self db_trace_self_wrapper() at db_trace_self_wrapper+0x38 kdb_backtrace() at kdb_backtrace+0x2c vpanic() at vpanic+0x154 panic() at panic+0x2a page_fault_handler() at page_fault_handler+0x1ee do_trap_supervisor() at do_trap_supervisor+0x76 cpu_exception_handler_supervisor() at cpu_exception_handler_supervisor+0x70 --- exception 13, tval =3D 0 nfsrvd_listxattr() at nfsrvd_listxattr+0x306 nfsrvd_dorpc() at nfsrvd_dorpc+0x154c nfssvc_program() at nfssvc_program+0x5a4 svc_run_internal() at svc_run_internal+0x808 svc_run() at svc_run+0x1a8 nfsrvd_nfsd() at nfsrvd_nfsd+0x30e nfssvc_nfsd() at nfssvc_nfsd+0x386 sys_nfssvc() at sys_nfssvc+0xd0 do_trap_user() at do_trap_user+0x206 cpu_exception_handler_user() at cpu_exception_handler_user+0x72 --- exception 8, tval =3D 0 --=20 You are receiving this mail because: You are the assignee for the bug.=
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