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/verity/pagecache.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 80 insertions(+) create mode 100644 fs/verity/pagecache.c (limited to 'fs/verity/pagecache.c') diff --git a/fs/verity/pagecache.c b/fs/verity/pagecache.c new file mode 100644 index 000000000..99f5f53ee --- /dev/null +++ b/fs/verity/pagecache.c @@ -0,0 +1,80 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright 2019 Google LLC + */ +#include "fsverity_private.h" + +#include +#include +#include + +/** + * generic_read_merkle_tree_page - generic ->read_merkle_tree_page helper + * @inode: inode containing the Merkle tree + * @index: 0-based index of the Merkle tree page in the inode + * + * The caller needs to adjust @index from the Merkle-tree relative index passed + * to ->read_merkle_tree_page to the actual index where the Merkle tree is + * stored in the page cache for @inode. + */ +struct page *generic_read_merkle_tree_page(struct inode *inode, pgoff_t index) +{ + struct folio *folio; + + folio = read_mapping_folio(inode->i_mapping, index, NULL); + if (IS_ERR(folio)) + return ERR_CAST(folio); + return folio_file_page(folio, index); +} +EXPORT_SYMBOL_GPL(generic_read_merkle_tree_page); + +/** + * generic_readahead_merkle_tree() - generic ->readahead_merkle_tree helper + * @inode: inode containing the Merkle tree + * @index: 0-based index of the first Merkle tree page to read ahead in the + * inode + * @nr_pages: the number of Merkle tree pages that should be read ahead + * + * The caller needs to adjust @index from the Merkle-tree relative index passed + * to ->read_merkle_tree_page to the actual index where the Merkle tree is + * stored in the page cache for @inode. + */ +void generic_readahead_merkle_tree(struct inode *inode, pgoff_t index, + unsigned long nr_pages) +{ + struct folio *folio; + + lockdep_assert_held(&inode->i_mapping->invalidate_lock); + + folio = __filemap_get_folio(inode->i_mapping, index, FGP_ACCESSED, 0); + if (folio == ERR_PTR(-ENOENT) || + (!IS_ERR(folio) && !folio_test_uptodate(folio))) { + DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, index); + + page_cache_ra_unbounded(&ractl, nr_pages, 0); + } + if (!IS_ERR(folio)) + folio_put(folio); +} +EXPORT_SYMBOL_GPL(generic_readahead_merkle_tree); + +/** + * fsverity_fill_zerohash() - fill folio with hashes of zero data block + * @folio: folio to fill + * @offset: offset in the folio to start + * @len: length of the range to fill with hashes + * @vi: fsverity info + */ +void fsverity_fill_zerohash(struct folio *folio, size_t offset, size_t len, + struct fsverity_info *vi) +{ + size_t off = offset; + + WARN_ON_ONCE(!IS_ALIGNED(offset, vi->tree_params.digest_size)); + WARN_ON_ONCE(!IS_ALIGNED(len, vi->tree_params.digest_size)); + + for (; off < (offset + len); off += vi->tree_params.digest_size) + memcpy_to_folio(folio, off, vi->tree_params.zero_digest, + vi->tree_params.digest_size); +} +EXPORT_SYMBOL_GPL(fsverity_fill_zerohash); -- cgit v1.3.1