Date: Tue, 23 Nov 2021 16:48:26 +0000 From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 259996] bad CREATE_SESSION NFS v4.1 reply can cause client kernel page fault Message-ID: <bug-259996-227@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D259996 Bug ID: 259996 Summary: bad CREATE_SESSION NFS v4.1 reply can cause client kernel page fault 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 #229673 text/plain mime type: Created attachment 229673 --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=3D229673&action= =3Dedit Demo that crashes an NFS client. These lines in nfsrpc_createsession() irdcnt =3D fxdr_unsigned(int, *tl); if (irdcnt > 0) NFSM_DISSECT(tl, uint32_t *, irdcnt * NFSX_UNSIGNED= ); will accept the server's irdcount if it's huge and positive, but can then pass a negative size due to overflow in the multiply. This can cause nfsm_dissect() to subtract a big number from nd->nd_dpos, which causes a wild pointer reference next time nd->nd_dpos is used. I've attached a demo: # uname -a FreeBSD 14.0-CURRENT FreeBSD 14.0-CURRENT #91 main-n250901-77e3db078984-di= rty: Tue Nov 23 10:48:40 EST 2021=20=20=20=20 rtm@xxx:/usr/obj/usr/rtm/symbsd/src/riscv.riscv64/sys/RTM riscv # cc fnfs_1.c # ./a.out ... panic: Fatal page fault at 0xffffffc000227d16: 0xffffffcf82b289c8 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 0xffffffcf82b289c8 nfsrpc_createsession() at nfsrpc_createsession+0x730 nfsrpc_setclient() at nfsrpc_setclient+0x240 nfscl_getcl() at nfscl_getcl+0x53e mountnfs() at mountnfs+0x722 nfs_mount() at nfs_mount+0x161e vfs_mount_sigdefer() at vfs_mount_sigdefer+0x20 vfs_domount_first() at vfs_domount_first+0x1d4 vfs_domount() at vfs_domount+0x21c vfs_donmount() at vfs_donmount+0x79c sys_nmount() at sys_nmount+0x66 do_trap_user() at do_trap_user+0x206 cpu_exception_handler_user() at cpu_exception_handler_user+0x72 --=20 You are receiving this mail because: You are the assignee for the bug.=
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