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authorDaniel Borkmann <daniel@iogearbox.net>2019-11-02 00:17:56 +0100
committerAlexei Starovoitov <ast@kernel.org>2019-11-02 12:39:12 -0700
commit1d1585ca0f48fe7ed95c3571f3e4a82b2b5045dc (patch)
tree0e36ebafa09168d30407e3b5fb06905647f91262 /mm
parente1cb7d2d60d536baf24d2f0fd58786324ce92331 (diff)
downloadlinux-1d1585ca0f48fe7ed95c3571f3e4a82b2b5045dc.tar.bz2
uaccess: Add non-pagefault user-space write function
Commit 3d7081822f7f ("uaccess: Add non-pagefault user-space read functions") missed to add probe write function, therefore factor out a probe_write_common() helper with most logic of probe_kernel_write() except setting KERNEL_DS, and add a new probe_user_write() helper so it can be used from BPF side. Again, on some archs, the user address space and kernel address space can co-exist and be overlapping, so in such case, setting KERNEL_DS would mean that the given address is treated as being in kernel address space. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Andrii Nakryiko <andriin@fb.com> Cc: Masami Hiramatsu <mhiramat@kernel.org> Link: https://lore.kernel.org/bpf/9df2542e68141bfa3addde631441ee45503856a8.1572649915.git.daniel@iogearbox.net
Diffstat (limited to 'mm')
-rw-r--r--mm/maccess.c45
1 files changed, 41 insertions, 4 deletions
diff --git a/mm/maccess.c b/mm/maccess.c
index d065736f6b87..2d3c3d01064c 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -18,6 +18,18 @@ probe_read_common(void *dst, const void __user *src, size_t size)
return ret ? -EFAULT : 0;
}
+static __always_inline long
+probe_write_common(void __user *dst, const void *src, size_t size)
+{
+ long ret;
+
+ pagefault_disable();
+ ret = __copy_to_user_inatomic(dst, src, size);
+ pagefault_enable();
+
+ return ret ? -EFAULT : 0;
+}
+
/**
* probe_kernel_read(): safely attempt to read from a kernel-space location
* @dst: pointer to the buffer that shall take the data
@@ -85,6 +97,7 @@ EXPORT_SYMBOL_GPL(probe_user_read);
* Safely write to address @dst from the buffer at @src. If a kernel fault
* happens, handle that and return -EFAULT.
*/
+
long __weak probe_kernel_write(void *dst, const void *src, size_t size)
__attribute__((alias("__probe_kernel_write")));
@@ -94,15 +107,39 @@ long __probe_kernel_write(void *dst, const void *src, size_t size)
mm_segment_t old_fs = get_fs();
set_fs(KERNEL_DS);
- pagefault_disable();
- ret = __copy_to_user_inatomic((__force void __user *)dst, src, size);
- pagefault_enable();
+ ret = probe_write_common((__force void __user *)dst, src, size);
set_fs(old_fs);
- return ret ? -EFAULT : 0;
+ return ret;
}
EXPORT_SYMBOL_GPL(probe_kernel_write);
+/**
+ * probe_user_write(): safely attempt to write to a user-space location
+ * @dst: address to write to
+ * @src: pointer to the data that shall be written
+ * @size: size of the data chunk
+ *
+ * Safely write to address @dst from the buffer at @src. If a kernel fault
+ * happens, handle that and return -EFAULT.
+ */
+
+long __weak probe_user_write(void __user *dst, const void *src, size_t size)
+ __attribute__((alias("__probe_user_write")));
+
+long __probe_user_write(void __user *dst, const void *src, size_t size)
+{
+ long ret = -EFAULT;
+ mm_segment_t old_fs = get_fs();
+
+ set_fs(USER_DS);
+ if (access_ok(dst, size))
+ ret = probe_write_common(dst, src, size);
+ set_fs(old_fs);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(probe_user_write);
/**
* strncpy_from_unsafe: - Copy a NUL terminated string from unsafe address.