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/cachefiles/volume.c | 141 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 141 insertions(+) create mode 100644 fs/cachefiles/volume.c (limited to 'fs/cachefiles/volume.c') diff --git a/fs/cachefiles/volume.c b/fs/cachefiles/volume.c new file mode 100644 index 000000000..6c0da6136 --- /dev/null +++ b/fs/cachefiles/volume.c @@ -0,0 +1,141 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* Volume handling. + * + * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include +#include +#include +#include "internal.h" +#include + +/* + * Allocate and set up a volume representation. We make sure all the fanout + * directories are created and pinned. + */ +void cachefiles_acquire_volume(struct fscache_volume *vcookie) +{ + struct cachefiles_volume *volume; + struct cachefiles_cache *cache = vcookie->cache->cache_priv; + const struct cred *saved_cred; + struct dentry *vdentry, *fan; + size_t len; + char *name; + bool is_new = false; + int ret, n_accesses, i; + + _enter(""); + + volume = kzalloc_obj(struct cachefiles_volume); + if (!volume) + return; + volume->vcookie = vcookie; + volume->cache = cache; + INIT_LIST_HEAD(&volume->cache_link); + + cachefiles_begin_secure(cache, &saved_cred); + + len = vcookie->key[0]; + name = kmalloc(len + 3, GFP_NOFS); + if (!name) + goto error_vol; + name[0] = 'I'; + memcpy(name + 1, vcookie->key + 1, len); + name[len + 1] = 0; + +retry: + vdentry = cachefiles_get_directory(cache, cache->store, name, &is_new); + if (IS_ERR(vdentry)) + goto error_name; + volume->dentry = vdentry; + + if (is_new) { + if (!cachefiles_set_volume_xattr(volume)) + goto error_dir; + } else { + ret = cachefiles_check_volume_xattr(volume); + if (ret < 0) { + if (ret != -ESTALE) + goto error_dir; + vdentry = start_removing_dentry(cache->store, vdentry); + if (!IS_ERR(vdentry)) + cachefiles_bury_object(cache, NULL, cache->store, + vdentry, + FSCACHE_VOLUME_IS_WEIRD); + cachefiles_put_directory(volume->dentry); + cond_resched(); + goto retry; + } + } + + for (i = 0; i < 256; i++) { + sprintf(name, "@%02x", i); + fan = cachefiles_get_directory(cache, vdentry, name, NULL); + if (IS_ERR(fan)) + goto error_fan; + volume->fanout[i] = fan; + } + + cachefiles_end_secure(cache, saved_cred); + + vcookie->cache_priv = volume; + n_accesses = atomic_inc_return(&vcookie->n_accesses); /* Stop wakeups on dec-to-0 */ + trace_fscache_access_volume(vcookie->debug_id, 0, + refcount_read(&vcookie->ref), + n_accesses, fscache_access_cache_pin); + + spin_lock(&cache->object_list_lock); + list_add(&volume->cache_link, &volume->cache->volumes); + spin_unlock(&cache->object_list_lock); + + kfree(name); + return; + +error_fan: + for (i = 0; i < 256; i++) + cachefiles_put_directory(volume->fanout[i]); +error_dir: + cachefiles_put_directory(volume->dentry); +error_name: + kfree(name); +error_vol: + kfree(volume); + cachefiles_end_secure(cache, saved_cred); +} + +/* + * Release a volume representation. + */ +static void __cachefiles_free_volume(struct cachefiles_volume *volume) +{ + int i; + + _enter(""); + + volume->vcookie->cache_priv = NULL; + + for (i = 0; i < 256; i++) + cachefiles_put_directory(volume->fanout[i]); + cachefiles_put_directory(volume->dentry); + kfree(volume); +} + +void cachefiles_free_volume(struct fscache_volume *vcookie) +{ + struct cachefiles_volume *volume = vcookie->cache_priv; + + if (volume) { + spin_lock(&volume->cache->object_list_lock); + list_del_init(&volume->cache_link); + spin_unlock(&volume->cache->object_list_lock); + __cachefiles_free_volume(volume); + } +} + +void cachefiles_withdraw_volume(struct cachefiles_volume *volume) +{ + cachefiles_set_volume_xattr(volume); + __cachefiles_free_volume(volume); +} -- cgit v1.3.1