From 78004e9a87f240df03e2f73120d291763c32e0a7 Mon Sep 17 00:00:00 2001 From: Ali Ahmet Memis Date: Fri, 21 Aug 2026 01:45:27 +0000 Subject: openrisc: fix arbitrary kernel memory access via or1k_atomic syscall sys_or1k_atomic() (syscall 244 in the "or1k" ABI) takes two user pointers, v1 and v2, and swaps the words they point to in hand-written assembly. l.lwz r29,0(r4) l.lwz r27,0(r5) l.sw 0(r4),r27 l.sw 0(r5),r29 The pointers are not checked with access_ok(). The four memory accesses also have no exception table entries. A caller passes a kernel address as either pointer, and the syscall reads from and writes to it directly. This gives an unprivileged process a kernel read/write primitive. It overwrites kernel data such as the sys_call_table, gaining code execution in kernel context. Check both pointers before entering the critical section. Add fixups for the four memory accesses so faults on valid but unmapped user addresses return -EFAULT. [shorne@gmail.com: fix comment style] Fixes: 9d02a4283e9c ("OpenRISC: Boot code") Cc: stable@vger.kernel.org Signed-off-by: Ali Ahmet Memis Signed-off-by: Stafford Horne --- fs/nfsd/auth.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 89 insertions(+) create mode 100644 fs/nfsd/auth.c (limited to 'fs/nfsd/auth.c') diff --git a/fs/nfsd/auth.c b/fs/nfsd/auth.c new file mode 100644 index 000000000..4dc327e02 --- /dev/null +++ b/fs/nfsd/auth.c @@ -0,0 +1,89 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (C) 1995, 1996 Olaf Kirch */ + +#include +#include "nfsd.h" +#include "auth.h" + +int nfsexp_flags(struct svc_cred *cred, struct svc_export *exp) +{ + struct exp_flavor_info *f; + struct exp_flavor_info *end = exp->ex_flavors + exp->ex_nflavors; + + for (f = exp->ex_flavors; f < end; f++) { + if (f->pseudoflavor == cred->cr_flavor) + return f->flags; + } + return exp->ex_flags; + +} + +int nfsd_setuser(struct svc_cred *cred, struct svc_export *exp) +{ + struct group_info *rqgi; + struct group_info *gi; + struct cred *new; + int i; + int flags = nfsexp_flags(cred, exp); + + /* discard any old override before preparing the new set */ + put_cred(revert_creds(get_cred(current_real_cred()))); + new = prepare_creds(); + if (!new) + return -ENOMEM; + + new->fsuid = cred->cr_uid; + new->fsgid = cred->cr_gid; + + rqgi = cred->cr_group_info; + + if (flags & NFSEXP_ALLSQUASH) { + new->fsuid = exp->ex_anon_uid; + new->fsgid = exp->ex_anon_gid; + gi = groups_alloc(0); + if (!gi) + goto oom; + } else if (flags & NFSEXP_ROOTSQUASH) { + if (uid_eq(new->fsuid, GLOBAL_ROOT_UID)) + new->fsuid = exp->ex_anon_uid; + if (gid_eq(new->fsgid, GLOBAL_ROOT_GID)) + new->fsgid = exp->ex_anon_gid; + + gi = groups_alloc(rqgi->ngroups); + if (!gi) + goto oom; + + for (i = 0; i < rqgi->ngroups; i++) { + if (gid_eq(GLOBAL_ROOT_GID, rqgi->gid[i])) + gi->gid[i] = exp->ex_anon_gid; + else + gi->gid[i] = rqgi->gid[i]; + } + + /* Each thread allocates its own gi, no race */ + groups_sort(gi); + } else { + gi = get_group_info(rqgi); + } + + if (uid_eq(new->fsuid, INVALID_UID)) + new->fsuid = exp->ex_anon_uid; + if (gid_eq(new->fsgid, INVALID_GID)) + new->fsgid = exp->ex_anon_gid; + + set_groups(new, gi); + put_group_info(gi); + + if (!uid_eq(new->fsuid, GLOBAL_ROOT_UID)) + new->cap_effective = cap_drop_nfsd_set(new->cap_effective); + else + new->cap_effective = cap_raise_nfsd_set(new->cap_effective, + new->cap_permitted); + put_cred(override_creds(new)); + return 0; + +oom: + abort_creds(new); + return -ENOMEM; +} + -- cgit v1.3.1