sendfile08 - initialize buf structure

PATCH In review Helge Deller 2 participants 2 messages Nov 6, 2013

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Helge Deller

author

2013-11-06 19:41 UTC #0 lore raw

PATCH 1/1 sendfile08 - initialize buf structure

The sendfile08 testcase uses the sendfile() syscall to write the strings "hello" and "world" to a file descriptor and then reads them back in through another file descriptor.

The length of the strings written are determined by strlen(), so that in total 10 bytes are written.

When reading the strings back in, again 10 bytes are read, but the problem is, that those are read back into a *local* string buffer array (buf[]) which hasn't been initialized.

Afterwards,
strcmp(buf, "helloworld")
is called to compare input and output.
This strcmp() is wrong, because basically "helloworld\0" (with the trailing string zero terminator) is compared to "helloworld" (likely without a trailing zero in the buf[] array).

So, if buf[] hasn't been initialized, it's not guaranteed that the 10th byte in buf[10] equals to '\0'.

This problem was found on hppa64-linux-gnu architecture, most likely, because it's a stack-grows-up architecture.

Fix this buglet, by zero-initializing the buf[] array. Alternatively, strncmp() could be used instead of memcmp().

Signed-off-by Helge Deller <[email protected]>

testcases/kernel/syscalls/sendfile/sendfile08.c renamed from testcases/kernel/syscalls/sendfile/sendfile08.c.org +2 -0

@@ -74,6 +74,8 @@ int main(int argc, char *argv[])
 		if (ret == -1)
 			tst_brkm(TBROK | TERRNO, cleanup, "lseek %s failed",
 				 out_file);
+
+		memset(buf, 0, BUFSIZ);
 		ret = read(out_fd, buf, BUFSIZ);
 		if (ret == -1)
 			tst_brkm(TBROK | TERRNO, cleanup, "read %s failed",

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Jan Stancek

2013-11-06 21:13 UTC #1 lore raw

----- Original Message -----

Quoted 26 lines

From: "Helge Deller" <[email protected]>
To: [email protected]
Sent: Wednesday, 6 November, 2013 8:41:11 PM
Subject: [LTP] [PATCH] sendfile08 - initialize buf structure
The sendfile08 testcase uses the sendfile() syscall to write the strings "hello" and "world" to a file descriptor and then reads them back in through another file descriptor.
The length of the strings written are determined by strlen(), so that in total 10 bytes are written.
When reading the strings back in, again 10 bytes are read, but the problem is, that those are read back into a *local* string buffer array (buf[]) which hasn't been initialized.
Afterwards,
strcmp(buf, "helloworld")
is called to compare input and output.
This strcmp() is wrong, because basically "helloworld\0" (with the trailing string zero terminator) is compared to "helloworld" (likely without a trailing zero in the buf[] array).
So, if buf[] hasn't been initialized, it's not guaranteed that the 10th byte in buf[10] equals to '\0'.

Quoted 7 lines

This problem was found on hppa64-linux-gnu architecture, most likely, because it's a stack-grows-up architecture.
Fix this buglet, by zero-initializing the buf[] array. Alternatively, strncmp() could be used instead of memcmp().
Signed-off-by Helge Deller <[email protected]>

Hi,

I pushed the strncmp() version.

Thanks,
Jan

Quoted 12 lines

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November Webinars for C, C++, Fortran Developers
Accelerate application performance with scalable programming models. Explore techniques for threading, error checking, porting, and tuning. Get the most from the latest Intel processors and coprocessors. See abstracts and register
http://pubads.g.doubleclick.net/gampad/clk?id=60136231&iu=/4140/ostg.clktrk
_______________________________________________
Ltp-list mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/ltp-list