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/proc/self.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 66 insertions(+) create mode 100644 fs/proc/self.c (limited to 'fs/proc/self.c') diff --git a/fs/proc/self.c b/fs/proc/self.c new file mode 100644 index 000000000..56adf1c68 --- /dev/null +++ b/fs/proc/self.c @@ -0,0 +1,66 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include "internal.h" + +/* + * /proc/self: + */ +static const char *proc_self_get_link(struct dentry *dentry, + struct inode *inode, + struct delayed_call *done) +{ + struct pid_namespace *ns = proc_pid_ns(inode->i_sb); + pid_t tgid = task_tgid_nr_ns(current, ns); + char *name; + + if (!tgid) + return ERR_PTR(-ENOENT); + /* max length of unsigned int in decimal + NULL term */ + name = kmalloc(10 + 1, dentry ? GFP_KERNEL : GFP_ATOMIC); + if (unlikely(!name)) + return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD); + sprintf(name, "%u", tgid); + set_delayed_call(done, kfree_link, name); + return name; +} + +static const struct inode_operations proc_self_inode_operations = { + .get_link = proc_self_get_link, +}; + +unsigned self_inum __ro_after_init; + +int proc_setup_self(struct super_block *s) +{ + struct dentry *self; + int ret = -ENOMEM; + + self = d_alloc_name(s->s_root, "self"); + if (self) { + struct inode *inode = new_inode(s); + if (inode) { + inode->i_ino = self_inum; + simple_inode_init_ts(inode); + inode->i_mode = S_IFLNK | S_IRWXUGO; + inode->i_uid = GLOBAL_ROOT_UID; + inode->i_gid = GLOBAL_ROOT_GID; + inode->i_op = &proc_self_inode_operations; + d_make_persistent(self, inode); + ret = 0; + } + dput(self); + } + + if (ret) + pr_err("proc_fill_super: can't allocate /proc/self\n"); + + return ret; +} + +void __init proc_self_init(void) +{ + proc_alloc_inum(&self_inum); +} -- cgit v1.3.1