linux-kernel - [PATCH 10/10] binfmt_flat: allow compressed flat binary format to work on MMU systems

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Message-Id: <1468358862-11799-11-git-send-email-nicolas.pitre@linaro.org>
Date:	Tue, 12 Jul 2016 17:27:42 -0400
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	Alexander Viro <viro@...iv.linux.org.uk>,
	David Howells <dhowells@...hat.com>,
	Greg Ungerer <gerg@...ux-m68k.org>
Subject: [PATCH  10/10] binfmt_flat: allow compressed flat binary format to work on MMU systems

Let's take the simple and obvious approach by decompressing the binary
into a kernel buffer and then copying it to user space.  Those who are
looking for more performance on a MMU system are unlikely to choose this
executable format anyway.

Signed-off-by: Nicolas Pitre <nico@...aro.org>
---
 fs/binfmt_flat.c | 44 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 42 insertions(+), 2 deletions(-)

diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
index 4cb0c4b6ae..24deae4dcb 100644
--- a/fs/binfmt_flat.c
+++ b/fs/binfmt_flat.c
@@ -35,6 +35,7 @@
 #include <linux/init.h>
 #include <linux/flat.h>
 #include <linux/syscalls.h>
+#include <linux/vmalloc.h>
 
 #include <asm/byteorder.h>
 #include <asm/uaccess.h>
@@ -637,6 +638,7 @@ static int load_flat_file(struct linux_binprm * bprm,
 		 * load it all in and treat it like a RAM load from now on
 		 */
 		if (flags & FLAT_FLAG_GZIP) {
+#ifndef CONFIG_MMU
 			result = decompress_exec(bprm, sizeof (struct flat_hdr),
 					 (((char *) textpos) + sizeof (struct flat_hdr)),
 					 (text_len + full_data
@@ -644,14 +646,52 @@ static int load_flat_file(struct linux_binprm * bprm,
 					 0);
 			memmove((void *) datapos, (void *) realdatastart,
 					full_data);
+#else
+			/*
+			 * This is used on MMU systems mainly for testing.
+			 * Let's use a kernel buffer to simplify things.
+			 */
+			long unz_text_len = text_len - sizeof(struct flat_hdr);
+			long unz_len = unz_text_len + full_data;
+			char *unz_data = vmalloc(unz_len);
+			if (!unz_data) {
+				result = -ENOMEM;
+			} else {
+				result = decompress_exec(bprm, sizeof(struct flat_hdr),
+							 unz_data, unz_len, 0);
+				if (result == 0 &&
+				    (copy_to_user((void __user *)textpos + sizeof(struct flat_hdr),
+						  unz_data, unz_text_len) ||
+				     copy_to_user((void __user *)datapos,
+				    		  unz_data + unz_text_len, full_data)))
+					result = -EFAULT;
+				vfree(unz_data);
+			}
+#endif
 		} else if (flags & FLAT_FLAG_GZDATA) {
 			result = read_code(bprm->file, textpos, 0, text_len);
-			if (!IS_ERR_VALUE(result))
+			if (!IS_ERR_VALUE(result)) {
+#ifndef CONFIG_MMU
 				result = decompress_exec(bprm, text_len, (char *) datapos,
 						 full_data, 0);
+#else
+				char *unz_data = vmalloc(full_data);
+				if (!unz_data) {
+					result = -ENOMEM;
+				} else {
+					result = decompress_exec(bprm, text_len,
+						       unz_data, full_data, 0);
+					if (result == 0 &&
+					    copy_to_user((void __user *)datapos,
+						         unz_data, full_data))
+						result = -EFAULT;
+					vfree(unz_data);
+				}
+#endif
+			}
 		}
 		else
-#endif
+#endif /* CONFIG_BINFMT_ZFLAT */
 		{
 			result = read_code(bprm->file, textpos, 0, text_len);
 			if (!IS_ERR_VALUE(result))
-- 
2.7.4