| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-Id: <155110354092.21156.13871336589042178985.stgit@devbox>
Date: Mon, 25 Feb 2019 23:05:41 +0900
From: Masami Hiramatsu <mhiramat@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>,
Linus Torvalds <torvalds@...ux-foundation.org>
Cc: mhiramat@...nel.org, linux-kernel@...r.kernel.org,
Andy Lutomirski <luto@...capital.net>,
Ingo Molnar <mingo@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Changbin Du <changbin.du@...il.com>,
Jann Horn <jannh@...gle.com>,
Kees Cook <keescook@...omium.org>,
Andy Lutomirski <luto@...nel.org>,
Alexei Starovoitov <alexei.starovoitov@...il.com>,
Nadav Amit <namit@...are.com>,
Peter Zijlstra <peterz@...radead.org>
Subject: [RFC PATCH 2/4] uaccess: Add non-pagefault user-space read functions
Add probe_user_read() and strncpy_from_unsafe_user() which
will not involves mm_sem so we can use it for accessing
user-space in irq-handler.
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
include/linux/uaccess.h | 13 +++++
mm/maccess.c | 134 +++++++++++++++++++++++++++++++++++++++++------
2 files changed, 131 insertions(+), 16 deletions(-)
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 37b226e8df13..906573b8f02c 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -240,6 +240,17 @@ extern long probe_kernel_read(void *dst, const void *src, size_t size);
extern long __probe_kernel_read(void *dst, const void *src, size_t size);
/*
+ * probe_user_read(): safely attempt to read from a location in user space
+ * @dst: pointer to the buffer that shall take the data
+ * @src: address to read from
+ * @size: size of the data chunk
+ *
+ * Safely read from address @src to the buffer at @dst. If a kernel fault
+ * happens, handle that and return -EFAULT.
+ */
+extern long probe_user_read(void *dst, const void __user *src, size_t size);
+
+/*
* probe_kernel_write(): safely attempt to write to a location
* @dst: address to write to
* @src: pointer to the data that shall be written
@@ -252,6 +263,8 @@ extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);
extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size);
extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count);
+extern long strncpy_from_unsafe_user(char *dst, const void __user *unsafe_addr,
+ long count);
/**
* probe_kernel_address(): safely attempt to read from a location
diff --git a/mm/maccess.c b/mm/maccess.c
index 7a9752d59587..7d38d783e0b1 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -5,8 +5,20 @@
#include <linux/mm.h>
#include <linux/uaccess.h>
+static __always_inline long
+probe_read_common(void *dst, const void __user *src, size_t size)
+{
+ long ret;
+
+ pagefault_disable();
+ ret = __copy_from_user_inatomic(dst, src, size);
+ pagefault_enable();
+
+ return ret ? -EFAULT : 0;
+}
+
/**
- * probe_kernel_read(): safely attempt to read from a location
+ * probe_kernel_read(): safely attempt to read from a kernel-space location
* @dst: pointer to the buffer that shall take the data
* @src: address to read from
* @size: size of the data chunk
@@ -30,18 +42,53 @@ long __probe_kernel_read(void *dst, const void *src, size_t size)
set_fs(KERNEL_DS);
current->kernel_uaccess_faults_ok++;
- pagefault_disable();
- ret = __copy_from_user_inatomic(dst,
- (__force const void __user *)src, size);
- pagefault_enable();
+ ret = probe_read_common(dst, (__force const void __user *)src, size);
current->kernel_uaccess_faults_ok--;
set_fs(old_fs);
- return ret ? -EFAULT : 0;
+ return ret;
}
EXPORT_SYMBOL_GPL(probe_kernel_read);
/**
+ * probe_user_read(): safely attempt to read from a user-space location
+ * @dst: pointer to the buffer that shall take the data
+ * @src: address to read from. This must be a user address.
+ * @size: size of the data chunk
+ *
+ * Safely read from user address @src to the buffer at @dst. If a kernel fault
+ * happens, handle that and return -EFAULT.
+ */
+
+long __weak probe_user_read(void *dst, const void __user *src, size_t size)
+ __attribute__((alias("__probe_user_read")));
+
+static long __normal_probe_user_read(void *dst, const void __user *src,
+ size_t size)
+{
+ if (!access_ok(src, size))
+ return -EFAULT;
+
+ return probe_read_common(dst, src, size);
+}
+
+long __probe_user_read(void *dst, const void __user *src, size_t size)
+{
+ long ret;
+ mm_segment_t old_fs = get_fs();
+
+ if (segment_eq(old_fs, USER_DS)) {
+ ret = __normal_probe_user_read(dst, src, size);
+ } else {
+ set_fs(USER_DS);
+ ret = __normal_probe_user_read(dst, src, size);
+ set_fs(old_fs);
+ }
+ return ret ? -EFAULT : 0;
+}
+EXPORT_SYMBOL_GPL(probe_user_read);
+
+/**
* probe_kernel_write(): safely attempt to write to a location
* @dst: address to write to
* @src: pointer to the data that shall be written
@@ -70,6 +117,22 @@ long __probe_kernel_write(void *dst, const void *src, size_t size)
}
EXPORT_SYMBOL_GPL(probe_kernel_write);
+
+static __always_inline long strncpy_from_unsafe_common(char *dst,
+ const char __user *unsafe_addr, long count)
+{
+ const char __user *src = unsafe_addr;
+ int ret;
+
+ pagefault_disable();
+ do {
+ ret = __get_user(*dst++, src++);
+ } while (dst[-1] && ret == 0 && src - unsafe_addr < count);
+ dst[-1] = '\0';
+ pagefault_enable();
+
+ return ret ? -EFAULT : src - unsafe_addr;
+}
/**
* strncpy_from_unsafe: - Copy a NUL terminated string from unsafe address.
* @dst: Destination address, in kernel space. This buffer must be at
@@ -90,7 +153,6 @@ EXPORT_SYMBOL_GPL(probe_kernel_write);
long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count)
{
mm_segment_t old_fs = get_fs();
- const void *src = unsafe_addr;
long ret;
if (unlikely(count <= 0))
@@ -98,16 +160,56 @@ long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count)
set_fs(KERNEL_DS);
current->kernel_uaccess_faults_ok++;
- pagefault_disable();
-
- do {
- ret = __get_user(*dst++, (const char __user __force *)src++);
- } while (dst[-1] && ret == 0 && src - unsafe_addr < count);
-
- dst[-1] = '\0';
- pagefault_enable();
+ ret = strncpy_from_unsafe_common(dst,
+ (const char __user __force *)unsafe_addr, count);
current->kernel_uaccess_faults_ok--;
set_fs(old_fs);
- return ret ? -EFAULT : src - unsafe_addr;
+ return ret;
+}
+
+static __always_inline long __strncpy_from_unsafe_user(char *dst,
+ const char __user *unsafe_addr, long count)
+{
+ if (!access_ok(unsafe_addr, count))
+ return -EFAULT;
+
+ return strncpy_from_unsafe_common(dst, unsafe_addr, count);
+}
+
+/**
+ * strncpy_from_unsafe_user: - Copy a NUL terminated string from unsafe user
+ * address.
+ * @dst: Destination address, in kernel space. This buffer must be at
+ * least @count bytes long.
+ * @unsafe_addr: Unsafe user address.
+ * @count: Maximum number of bytes to copy, including the trailing NUL.
+ *
+ * Copies a NUL-terminated string from unsafe user address to kernel buffer.
+ *
+ * On success, returns the length of the string INCLUDING the trailing NUL.
+ *
+ * If access fails, returns -EFAULT (some data may have been copied
+ * and the trailing NUL added).
+ *
+ * If @count is smaller than the length of the string, copies @count-1 bytes,
+ * sets the last byte of @dst buffer to NUL and returns @count.
+ */
+long strncpy_from_unsafe_user(char *dst, const void __user *unsafe_addr,
+ long count)
+{
+ mm_segment_t old_fs = get_fs();
+ long ret;
+
+ if (unlikely(count <= 0))
+ return 0;
+
+ if (segment_eq(old_fs, USER_DS)) {
+ ret = __strncpy_from_unsafe_user(dst, unsafe_addr, count);
+ } else {
+ set_fs(USER_DS);
+ ret = __strncpy_from_unsafe_user(dst, unsafe_addr, count);
+ set_fs(old_fs);
+ }
+ return ret;
}
Powered by blists - more mailing lists