[PATCH] 2.5.27 read_write - take 2

[Marcin Dalecki <dalecki@evision.ag>]

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Alan Cox wrote:
> On Mon, 2002-07-22 at 15:08, Marcin Dalecki wrote:
> 
>>- It is fixing completely confused wild casting to 32 bits.
>>
>>- Actually adding a comment explaining the obscure code, which is
>>   relying on integer arithmetics overflow.
> 
> 
> Better yet take the code from 2.4.19-rc3. The code you fixed up is still
> wrong. Sincie iov_len is not permitted to exceed 2Gb (SuS v3, found by
> the LSB test suite) the actual fix turns out to be even simpler and
> cleaner than the one you did

You are right. It makes sese, since readv and writev are
supposed to return ssize_t. Fixed patch version attached.



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diff -urN linux-2.5.27/fs/read_write.c linux/fs/read_write.c
--- linux-2.5.27/fs/read_write.c	2002-07-22 17:51:25.000000000 +0200
+++ linux/fs/read_write.c	2002-07-22 17:57:22.000000000 +0200
@@ -306,12 +306,16 @@
 	tot_len = 0;
 	ret = -EINVAL;
 	for (i = 0 ; i < count ; i++) {
-		size_t tmp = tot_len;
-		int len = iov[i].iov_len;
+		ssize_t tmp = tot_len;
+		ssize_t len = iov[i].iov_len;
+
+		/* check for SSIZE_MAX overflow */
 		if (len < 0)
 			goto out;
-		(u32)tot_len += len;
-		if (tot_len < tmp || tot_len < (u32)len)
+
+		tot_len += len;
+		/* check for overflows */
+		if (tot_len < tmp)
 			goto out;
 	}