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/befs/inode.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) create mode 100644 fs/befs/inode.c (limited to 'fs/befs/inode.c') diff --git a/fs/befs/inode.c b/fs/befs/inode.c new file mode 100644 index 000000000..791b46a6f --- /dev/null +++ b/fs/befs/inode.c @@ -0,0 +1,55 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * inode.c + * + * Copyright (C) 2001 Will Dyson + */ + +#include + +#include "befs.h" +#include "inode.h" + +/* + * Validates the correctness of the befs inode + * Returns BEFS_OK if the inode should be used, otherwise + * returns BEFS_BAD_INODE + */ +int +befs_check_inode(struct super_block *sb, befs_inode *raw_inode, + befs_blocknr_t inode) +{ + u32 magic1 = fs32_to_cpu(sb, raw_inode->magic1); + befs_inode_addr ino_num = fsrun_to_cpu(sb, raw_inode->inode_num); + u32 flags = fs32_to_cpu(sb, raw_inode->flags); + + /* check magic header. */ + if (magic1 != BEFS_INODE_MAGIC1) { + befs_error(sb, + "Inode has a bad magic header - inode = %lu", + (unsigned long)inode); + return BEFS_BAD_INODE; + } + + /* + * Sanity check2: inodes store their own block address. Check it. + */ + if (inode != iaddr2blockno(sb, &ino_num)) { + befs_error(sb, "inode blocknr field disagrees with vfs " + "VFS: %lu, Inode %lu", (unsigned long) + inode, (unsigned long)iaddr2blockno(sb, &ino_num)); + return BEFS_BAD_INODE; + } + + /* + * check flag + */ + + if (!(flags & BEFS_INODE_IN_USE)) { + befs_error(sb, "inode is not used - inode = %lu", + (unsigned long)inode); + return BEFS_BAD_INODE; + } + + return BEFS_OK; +} -- cgit v1.3.1