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 --- drivers/mtd/mtdblock_ro.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 80 insertions(+) create mode 100644 drivers/mtd/mtdblock_ro.c (limited to 'drivers/mtd/mtdblock_ro.c') diff --git a/drivers/mtd/mtdblock_ro.c b/drivers/mtd/mtdblock_ro.c new file mode 100644 index 000000000..e564521d6 --- /dev/null +++ b/drivers/mtd/mtdblock_ro.c @@ -0,0 +1,80 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Simple read-only (writable only for RAM) mtdblock driver + * + * Copyright © 2001-2010 David Woodhouse + */ + +#include +#include +#include +#include +#include +#include + +static int mtdblock_readsect(struct mtd_blktrans_dev *dev, + unsigned long block, char *buf) +{ + size_t retlen; + int err; + + err = mtd_read(dev->mtd, (block * 512), 512, &retlen, buf); + if (err && !mtd_is_bitflip(err)) + return 1; + return 0; +} + +static int mtdblock_writesect(struct mtd_blktrans_dev *dev, + unsigned long block, char *buf) +{ + size_t retlen; + + if (mtd_write(dev->mtd, (block * 512), 512, &retlen, buf)) + return 1; + return 0; +} + +static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd) +{ + struct mtd_blktrans_dev *dev = kzalloc_obj(*dev); + + if (!dev) + return; + + dev->mtd = mtd; + dev->devnum = mtd->index; + + dev->size = mtd->size >> 9; + dev->tr = tr; + dev->readonly = 1; + + if (mtd_type_is_nand(mtd)) + pr_warn_ratelimited("%s: MTD device '%s' is NAND, please consider using UBI block devices instead.\n", + tr->name, mtd->name); + + if (add_mtd_blktrans_dev(dev)) + kfree(dev); +} + +static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev) +{ + del_mtd_blktrans_dev(dev); +} + +static struct mtd_blktrans_ops mtdblock_tr = { + .name = "mtdblock", + .major = MTD_BLOCK_MAJOR, + .part_bits = 0, + .blksize = 512, + .readsect = mtdblock_readsect, + .writesect = mtdblock_writesect, + .add_mtd = mtdblock_add_mtd, + .remove_dev = mtdblock_remove_dev, + .owner = THIS_MODULE, +}; + +module_mtd_blktrans(mtdblock_tr); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("David Woodhouse "); +MODULE_DESCRIPTION("Simple read-only block device emulation access to MTD devices"); -- cgit v1.3.1