[LTP] [PATCH] ltp: Fix races in mmap1

[LTP] [PATCH] ltp: Fix races in mmap1

[Dave Kleikamp]

Make map_address a volatile pointer so that it is dereferenced in
read_mem() after read_lock is set.

Also read_lock must protect the verbose printf that reads from map_address
as well.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>

diff --git a/testcases/kernel/mem/mtest06/mmap1.c b/testcases/kernel/mem/mtest06/mmap1.c
index 7c80bb4..cd1127f 100644
--- a/testcases/kernel/mem/mtest06/mmap1.c
+++ b/testcases/kernel/mem/mtest06/mmap1.c
@@ -62,7 +62,7 @@
 } while (0)
 
 static int verbose_print = 0;
-static char *map_address;
+static char *volatile map_address;
 static jmp_buf jmpbuf;
 static volatile char read_lock = 0;
 
@@ -228,11 +228,13 @@ void *read_mem(void *ptr)
 				tst_resm(TINFO, "page fault occurred due to "
 					 "a read after an unmap");
 		} else {
-			if (verbose_print)
+			if (verbose_print) {
+				read_lock = 1;
 				tst_resm(TINFO,
 					 "read_mem(): content of memory: %s",
 					 (char *)map_address);
-
+				read_lock = 0;
+			}
 			for (j = 0; j < args[1]; j++) {
 				read_lock = 1;
 				if (map_address[j] != 'a')

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Re: [LTP] [PATCH] ltp: Fix races in mmap1

[Stanislav Kholmanskikh]

On 08/28/2013 05:07 PM, Dave Kleikamp wrote:
> Make map_address a volatile pointer so that it is dereferenced in
> read_mem() after read_lock is set.
>
> Also read_lock must protect the verbose printf that reads from map_address
> as well.
>
> Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
>
> diff --git a/testcases/kernel/mem/mtest06/mmap1.c b/testcases/kernel/mem/mtest06/mmap1.c
> index 7c80bb4..cd1127f 100644
> --- a/testcases/kernel/mem/mtest06/mmap1.c
> +++ b/testcases/kernel/mem/mtest06/mmap1.c
> @@ -62,7 +62,7 @@
>   } while (0)
>   
>   static int verbose_print = 0;
> -static char *map_address;
> +static char *volatile map_address;
>   static jmp_buf jmpbuf;
>   static volatile char read_lock = 0;
>   
> @@ -228,11 +228,13 @@ void *read_mem(void *ptr)
>   				tst_resm(TINFO, "page fault occurred due to "
>   					 "a read after an unmap");
>   		} else {
> -			if (verbose_print)
> +			if (verbose_print) {
> +				read_lock = 1;
>   				tst_resm(TINFO,
>   					 "read_mem(): content of memory: %s",
>   					 (char *)map_address);
> -
> +				read_lock = 0;
> +			}
>   			for (j = 0; j < args[1]; j++) {
>   				read_lock = 1;
>   				if (map_address[j] != 'a')
>
> ------------------------------------------------------------------------------
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Just in case.. To reproduce failures we need to invoke the test this 
way, for example:

   ./mmap1 -v -s 10

and then wait few minutes (it depends...)


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Re: [LTP] [PATCH] ltp: Fix races in mmap1

[chrubis]

Hi!
>  static int verbose_print = 0;
> -static char *map_address;
> +static char *volatile map_address;

Ok.

>  static jmp_buf jmpbuf;
>  static volatile char read_lock = 0;
>  
> @@ -228,11 +228,13 @@ void *read_mem(void *ptr)
>  				tst_resm(TINFO, "page fault occurred due to "
>  					 "a read after an unmap");
>  		} else {
> -			if (verbose_print)
> +			if (verbose_print) {
> +				read_lock = 1;
>  				tst_resm(TINFO,
>  					 "read_mem(): content of memory: %s",
>  					 (char *)map_address);
> -
> +				read_lock = 0;
> +			}
>  			for (j = 0; j < args[1]; j++) {
>  				read_lock = 1;
>  				if (map_address[j] != 'a')

Good catch, I've overlooked the tst_resm() when I was fixing the
testcase.

Commited, thanks.

-- 
Cyril Hrubis
chrubis@suse.cz

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