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authorChristoph Hellwig <hch@lst.de>2020-06-08 21:34:58 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-09 09:39:15 -0700
commitb58294ead14cde8081853487929adca821ed630d (patch)
treed32cbda4b476af7f21cca50c4eb58aee375bbbc1
parentfc3562d79456bf1740b44d84b8726d20de8d39bd (diff)
maccess: allow architectures to provide kernel probing directly
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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20200521152301.2587579-19-hch@lst.de Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/maccess.c76
1 files changed, 76 insertions, 0 deletions
diff --git a/mm/maccess.c b/mm/maccess.c
index 17b26bceb716..db7cf48d8fed 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -11,6 +11,81 @@ bool __weak probe_kernel_read_allowed(const void *unsafe_src, size_t size)
return true;
}
+#ifdef HAVE_GET_KERNEL_NOFAULT
+
+#define probe_kernel_read_loop(dst, src, len, type, err_label) \
+ while (len >= sizeof(type)) { \
+ __get_kernel_nofault(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(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)) { \
+ __put_kernel_nofault(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_nofault(char *dst, const void *unsafe_addr, long count)
+{
+ const void *src = unsafe_addr;
+
+ if (unlikely(count <= 0))
+ return 0;
+ if (!probe_kernel_read_allowed(unsafe_addr, count))
+ return -EFAULT;
+
+ pagefault_disable();
+ do {
+ __get_kernel_nofault(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_GET_KERNEL_NOFAULT */
/**
* probe_kernel_read(): safely attempt to read from kernel-space
* @dst: pointer to the buffer that shall take the data
@@ -113,6 +188,7 @@ long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
return ret ? -EFAULT : src - unsafe_addr;
}
+#endif /* HAVE_GET_KERNEL_NOFAULT */
/**
* probe_user_read(): safely attempt to read from a user-space location