From: Christoph Hellwig <hch@lst.de>
To: x86@kernel.org, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Masami Hiramatsu <mhiramat@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>
Cc: linux-parisc@vger.kernel.org, linux-um@lists.infradead.org,
netdev@vger.kernel.org, bpf@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: [PATCH 14/15] maccess: allow architectures to provide kernel probing directly
Date: Wed, 6 May 2020 08:22:22 +0200 [thread overview]
Message-ID: <20200506062223.30032-15-hch@lst.de> (raw)
In-Reply-To: <20200506062223.30032-1-hch@lst.de>
Provide alternative versions of probe_kernel_read, probe_kernel_write
and strncpy_from_kernel_unsafe that don't need set_fs magic, but instead
use arch hooks that are modelled after unsafe_{get,put}_user to access
kernel memory in an exception safe way.
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
mm/maccess.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 76 insertions(+)
diff --git a/mm/maccess.c b/mm/maccess.c
index aa59967d9b658..d99a5a67fa9b3 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -12,6 +12,81 @@ bool __weak probe_kernel_read_allowed(void *dst, const void *unsafe_src,
return true;
}
+#ifdef HAVE_ARCH_PROBE_KERNEL
+
+#define probe_kernel_read_loop(dst, src, len, type, err_label) \
+ while (len >= sizeof(type)) { \
+ arch_kernel_read(dst, src, type, err_label); \
+ dst += sizeof(type); \
+ src += sizeof(type); \
+ len -= sizeof(type); \
+ }
+
+long probe_kernel_read(void *dst, const void *src, size_t size)
+{
+ if (!probe_kernel_read_allowed(dst, src, size))
+ return -EFAULT;
+
+ pagefault_disable();
+ probe_kernel_read_loop(dst, src, size, u64, Efault);
+ probe_kernel_read_loop(dst, src, size, u32, Efault);
+ probe_kernel_read_loop(dst, src, size, u16, Efault);
+ probe_kernel_read_loop(dst, src, size, u8, Efault);
+ pagefault_enable();
+ return 0;
+Efault:
+ pagefault_enable();
+ return -EFAULT;
+}
+EXPORT_SYMBOL_GPL(probe_kernel_read);
+
+#define probe_kernel_write_loop(dst, src, len, type, err_label) \
+ while (len >= sizeof(type)) { \
+ arch_kernel_write(dst, src, type, err_label); \
+ dst += sizeof(type); \
+ src += sizeof(type); \
+ len -= sizeof(type); \
+ }
+
+long probe_kernel_write(void *dst, const void *src, size_t size)
+{
+ pagefault_disable();
+ probe_kernel_write_loop(dst, src, size, u64, Efault);
+ probe_kernel_write_loop(dst, src, size, u32, Efault);
+ probe_kernel_write_loop(dst, src, size, u16, Efault);
+ probe_kernel_write_loop(dst, src, size, u8, Efault);
+ pagefault_enable();
+ return 0;
+Efault:
+ pagefault_enable();
+ return -EFAULT;
+}
+
+long strncpy_from_kernel_unsafe(char *dst, const void *unsafe_addr, long count)
+{
+ const void *src = unsafe_addr;
+
+ if (unlikely(count <= 0))
+ return 0;
+ if (!probe_kernel_read_allowed(dst, unsafe_addr, count))
+ return -EFAULT;
+
+ pagefault_disable();
+ do {
+ arch_kernel_read(dst, src, u8, Efault);
+ dst++;
+ src++;
+ } while (dst[-1] && src - unsafe_addr < count);
+ pagefault_enable();
+
+ dst[-1] = '\0';
+ return src - unsafe_addr;
+Efault:
+ pagefault_enable();
+ dst[-1] = '\0';
+ return -EFAULT;
+}
+#else /* HAVE_ARCH_PROBE_KERNEL */
/**
* probe_kernel_read(): safely attempt to read from kernel-space
* @dst: pointer to the buffer that shall take the data
@@ -114,6 +189,7 @@ long strncpy_from_kernel_unsafe(char *dst, const void *unsafe_addr, long count)
return ret ? -EFAULT : src - unsafe_addr;
}
+#endif /* HAVE_ARCH_PROBE_KERNEL */
/**
* probe_user_read(): safely attempt to read from a user-space location
--
2.26.2
next prev parent reply other threads:[~2020-05-06 6:23 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-06 6:22 clean up and streamline probe_kernel_* and friends Christoph Hellwig
2020-05-06 6:22 ` [PATCH 01/15] maccess: unexport probe_kernel_write and probe_user_write Christoph Hellwig
2020-05-06 6:22 ` [PATCH 02/15] maccess: remove various unused weak aliases Christoph Hellwig
2020-05-06 6:22 ` [PATCH 03/15] maccess: remove duplicate kerneldoc commens Christoph Hellwig
2020-05-06 6:22 ` [PATCH 04/15] maccess: clarify kerneldoc comments Christoph Hellwig
2020-05-06 6:22 ` [PATCH 05/15] maccess: update the top of file comment Christoph Hellwig
2020-05-06 6:22 ` [PATCH 06/15] maccess: rename strncpy_from_unsafe_user to strncpy_from_user_unsafe Christoph Hellwig
2020-05-06 6:22 ` [PATCH 07/15] maccess: rename strncpy_from_unsafe_strict to strncpy_from_kernel_unsafe Christoph Hellwig
2020-05-06 6:22 ` [PATCH 08/15] maccess: rename strnlen_unsafe_user to strnlen_user_unsafe Christoph Hellwig
2020-05-06 17:44 ` Linus Torvalds
2020-05-06 17:47 ` Christoph Hellwig
2020-05-06 17:57 ` Linus Torvalds
2020-05-06 6:22 ` [PATCH 09/15] maccess: remove probe_read_common and probe_write_common Christoph Hellwig
2020-05-06 6:22 ` [PATCH 10/15] maccess: unify the probe kernel arch hooks Christoph Hellwig
2020-05-06 6:22 ` [PATCH 11/15] maccess: remove strncpy_from_unsafe Christoph Hellwig
2020-05-11 5:34 ` Masami Hiramatsu
2020-05-06 6:22 ` [PATCH 12/15] maccess: always use strict semantics for probe_kernel_read Christoph Hellwig
2020-05-11 5:05 ` Masami Hiramatsu
2020-05-11 5:27 ` Masami Hiramatsu
2020-05-06 6:22 ` [PATCH 13/15] maccess: move user access routines together Christoph Hellwig
2020-05-06 6:22 ` Christoph Hellwig [this message]
2020-05-06 6:22 ` [PATCH 15/15] x86: use non-set_fs based maccess routines Christoph Hellwig
2020-05-06 17:51 ` Linus Torvalds
2020-05-06 18:15 ` Christoph Hellwig
2020-05-06 19:01 ` Linus Torvalds
2020-05-07 5:12 ` Christoph Hellwig
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