[LTP] [PATCH v5] Refactor fork14 using new LTP API

[LTP] [PATCH v5] Refactor fork14 using new LTP API

[Andrea Cervesato]

From: Andrea Cervesato <andrea.cervesato@suse.com>

Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
.skip_in_compat usage
Fixed typos
Fixed license

 testcases/kernel/syscalls/fork/fork14.c | 205 +++++++++++-------------
 1 file changed, 92 insertions(+), 113 deletions(-)

diff --git a/testcases/kernel/syscalls/fork/fork14.c b/testcases/kernel/syscalls/fork/fork14.c
index 93af2ebac..421f2caa3 100644
--- a/testcases/kernel/syscalls/fork/fork14.c
+++ b/testcases/kernel/syscalls/fork/fork14.c
@@ -1,143 +1,122 @@
-/*********************************************************************
+// SPDX-License-Identifier: GPL-2.0-only
+/*
  * Copyright (C) 2014  Red Hat, Inc.
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of version 2 of the GNU General Public
- * License as published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it would be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
- *
- * Further, this software is distributed without any warranty that it
- * is free of the rightful claim of any third person regarding
- * infringement or the like.  Any license provided herein, whether
- * implied or otherwise, applies only to this software file.  Patent
- * licenses, if any, provided herein do not apply to combinations of
- * this program with other software, or any other product whatsoever.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
- * 02110-1301, USA.
+ * Copyright (C) 2023 SUSE LLC Andrea Cervesato <andrea.cervesato@suse.com>
+ */
+
+/*\
+ * [Description]
  *
  * This test is a reporducer for this patch:
- *              https://lkml.org/lkml/2012/4/24/328
+ * https://lore.kernel.org/lkml/1335289853-2923-1-git-send-email-siddhesh.poyarekar@gmail.com/
  * Since vma length in dup_mmap is calculated and stored in a unsigned
  * int, it will overflow when length of mmaped memory > 16 TB. When
- * overflow occur, fork will  incorrectly succeed. The patch above
- * fixed it.
- ********************************************************************/
+ * overflow occurs, fork will incorrectly succeed. The patch above fixed it.
+ */
 
-#include <sys/mman.h>
+#include "tst_test.h"
+#include <stdlib.h>
 #include <sys/wait.h>
-#include <stdio.h>
-#include <unistd.h>
-#include "test.h"
-#include "safe_macros.h"
-#include "lapi/abisize.h"
-
-char *TCID = "fork14";
-int TST_TOTAL = 1;
 
-#define GB		(1024 * 1024 * 1024L)
-
-/* set mmap threshold to 16TB */
 #define LARGE		(16 * 1024)
 #define EXTENT		(16 * 1024 + 10)
 
-static char **pointer_vec;
-
-static void setup(void);
-static void cleanup(void);
-static int  fork_test(void);
+static char **memvec;
 
-int main(int ac, char **av)
+static void run(void)
 {
-	int lc, reproduced;
+	int i, j, ret;
+	pid_t pid;
+	void *mem;
+	int prev_failed = 0;
+	int passed = 1;
+	int failures = 0;
 
-	tst_parse_opts(ac, av, NULL, NULL);
-/*
- * Tested on ppc64/x86_64/i386/s390x. And only 64bit has this issue.
- * Since a 32bit program can't mmap so many memory.
- */
-#ifdef TST_ABI32
-	tst_brkm(TCONF, NULL, "This test is only for 64bit.");
-#endif
-	setup();
-	for (lc = 0; TEST_LOOPING(lc); lc++) {
-		tst_count = 0;
-
-		reproduced = fork_test();
-		if (reproduced == 0)
-			tst_resm(TPASS, "fork failed as expected.");
-	}
-	cleanup();
-	tst_exit();
-}
+	for (i = 0; i < EXTENT; i++) {
+		mem = mmap(NULL, 1 * TST_GB,
+			PROT_READ | PROT_WRITE,
+			MAP_PRIVATE | MAP_ANONYMOUS,
+			0, 0);
 
-static void setup(void)
-{
-	tst_sig(FORK, DEF_HANDLER, cleanup);
-	TEST_PAUSE;
+		if (mem == MAP_FAILED) {
+			failures++;
 
-	pointer_vec = SAFE_MALLOC(cleanup, EXTENT * sizeof(char *));
-}
+			tst_res(TINFO, "mmap() failed");
 
-static void cleanup(void)
-{
-	free(pointer_vec);
-}
+			if (failures > 10) {
+				tst_brk(TCONF, "mmap() fails too many "
+					"times, so it's almost impossible to "
+					"get a vm_area_struct sized 16TB.");
+			}
 
-static int fork_test(void)
-{
-	int i, j, prev_failed = 0, fails = 0, cnt = 0;
-	int reproduced = 0;
-	void *addr;
+			continue;
+		}
 
-	for (i = 0; i < EXTENT; i++) {
-		addr = mmap(NULL, 1 * GB, PROT_READ | PROT_WRITE,
-			    MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
-		if (addr == MAP_FAILED) {
-			pointer_vec[i] = NULL;
-			fails++;
-			/*
-			 * EXTENT is "16*1024+10", if fails count exceeds 10,
-			 * we are almost impossible to get an vm_area_struct
-			 * sized 16TB
+		memvec[i] = mem;
+
+		pid = fork();
+
+		if (pid == -1) {
+			/* keep track of the failed fork() and verify that next one
+			 * is failing as well.
 			 */
-			if (fails == 11) {
-				tst_brkm(TCONF, cleanup, "mmap() fails too many"
-					 "times, so we are almost impossible to"
-					 " get an vm_area_struct sized 16TB.");
-			}
-		} else {
-			pointer_vec[i] = addr;
+			prev_failed = 1;
+			continue;
 		}
-		cnt++;
 
-		switch (tst_fork()) {
-		case -1:
-			prev_failed = 1;
-		break;
-		case 0:
+		if (!pid)
 			exit(0);
-		default:
-			SAFE_WAITPID(cleanup, -1, NULL, 0);
 
-			if (prev_failed > 0 && i >= LARGE) {
-				tst_resm(TFAIL, "Fork succeeds incorrectly");
-				reproduced = 1;
-				goto clear_memory_map;
-			}
+		ret = waitpid(pid, NULL, 0);
+		if (ret == -1 && errno != ECHILD)
+			tst_brk(TBROK | TERRNO, "waitpid() error");
+
+		if (prev_failed && i >= LARGE) {
+			passed = 0;
+			break;
 		}
+
+		prev_failed = 0;
+
+		tst_res(TINFO, "fork() passed at %d attempt", i);
 	}
 
-clear_memory_map:
-	for (j = 0; j < cnt; j++) {
-		if (pointer_vec[j])
-			SAFE_MUNMAP(cleanup, pointer_vec[j], 1 * GB);
+	for (j = 0; j < i; j++) {
+		if (memvec[j])
+			SAFE_MUNMAP(memvec[j], 1 * TST_GB);
 	}
 
-	return reproduced;
+	if (passed)
+		tst_res(TPASS, "fork() failed as expected");
+	else
+		tst_res(TFAIL, "fork() succeeded incorrectly");
 }
+
+static void setup(void)
+{
+	memvec = SAFE_MALLOC(EXTENT * sizeof(char *));
+	memset(memvec, 0, EXTENT);
+}
+
+static void cleanup(void)
+{
+	for (long i = 0; i < EXTENT; i++) {
+		if (memvec && memvec[i])
+			SAFE_MUNMAP(memvec[i], 1 * TST_GB);
+	}
+
+	if (memvec)
+		free(memvec);
+}
+
+static struct tst_test test = {
+	.test_all = run,
+	.setup = setup,
+	.cleanup = cleanup,
+	.forks_child = 1,
+	.skip_in_compat = 1,
+	.tags = (const struct tst_tag[]) {
+		{"linux-git", "7edc8b0ac16c"},
+		{}
+	}
+};
-- 
2.35.3


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Re: [LTP] [PATCH v5] Refactor fork14 using new LTP API

[Petr Vorel]

Hi Andrea,

Reviewed-by: Petr Vorel <pvorel@suse.cz>

Thanks!
Waiting for Cyril to have final look.

Kind regards,
Petr

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Re: [LTP] [PATCH v5] Refactor fork14 using new LTP API

[Martin Doucha]

Hi,
there's a stale pointer issue in memvec if you run the test with 
multiple iterations. See below.

On 22. 03. 24 10:04, Andrea Cervesato wrote:
> From: Andrea Cervesato <andrea.cervesato@suse.com>
> 
> Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
> ---
> .skip_in_compat usage
> Fixed typos
> Fixed license
> 
>   testcases/kernel/syscalls/fork/fork14.c | 205 +++++++++++-------------
>   1 file changed, 92 insertions(+), 113 deletions(-)
> 
> diff --git a/testcases/kernel/syscalls/fork/fork14.c b/testcases/kernel/syscalls/fork/fork14.c
> index 93af2ebac..421f2caa3 100644
> --- a/testcases/kernel/syscalls/fork/fork14.c
> +++ b/testcases/kernel/syscalls/fork/fork14.c
> @@ -1,143 +1,122 @@
> -/*********************************************************************
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
>    * Copyright (C) 2014  Red Hat, Inc.
> - *
> - * This program is free software; you can redistribute it and/or
> - * modify it under the terms of version 2 of the GNU General Public
> - * License as published by the Free Software Foundation.
> - *
> - * This program is distributed in the hope that it would be useful,
> - * but WITHOUT ANY WARRANTY; without even the implied warranty of
> - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> - *
> - * Further, this software is distributed without any warranty that it
> - * is free of the rightful claim of any third person regarding
> - * infringement or the like.  Any license provided herein, whether
> - * implied or otherwise, applies only to this software file.  Patent
> - * licenses, if any, provided herein do not apply to combinations of
> - * this program with other software, or any other product whatsoever.
> - *
> - * You should have received a copy of the GNU General Public License
> - * along with this program; if not, write the Free Software
> - * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
> - * 02110-1301, USA.
> + * Copyright (C) 2023 SUSE LLC Andrea Cervesato <andrea.cervesato@suse.com>
> + */
> +
> +/*\
> + * [Description]
>    *
>    * This test is a reporducer for this patch:
> - *              https://lkml.org/lkml/2012/4/24/328
> + * https://lore.kernel.org/lkml/1335289853-2923-1-git-send-email-siddhesh.poyarekar@gmail.com/
>    * Since vma length in dup_mmap is calculated and stored in a unsigned
>    * int, it will overflow when length of mmaped memory > 16 TB. When
> - * overflow occur, fork will  incorrectly succeed. The patch above
> - * fixed it.
> - ********************************************************************/
> + * overflow occurs, fork will incorrectly succeed. The patch above fixed it.
> + */
>   
> -#include <sys/mman.h>
> +#include "tst_test.h"
> +#include <stdlib.h>
>   #include <sys/wait.h>
> -#include <stdio.h>
> -#include <unistd.h>
> -#include "test.h"
> -#include "safe_macros.h"
> -#include "lapi/abisize.h"
> -
> -char *TCID = "fork14";
> -int TST_TOTAL = 1;
>   
> -#define GB		(1024 * 1024 * 1024L)
> -
> -/* set mmap threshold to 16TB */
>   #define LARGE		(16 * 1024)
>   #define EXTENT		(16 * 1024 + 10)
>   
> -static char **pointer_vec;
> -
> -static void setup(void);
> -static void cleanup(void);
> -static int  fork_test(void);
> +static char **memvec;
>   
> -int main(int ac, char **av)
> +static void run(void)
>   {
> -	int lc, reproduced;
> +	int i, j, ret;
> +	pid_t pid;
> +	void *mem;
> +	int prev_failed = 0;
> +	int passed = 1;
> +	int failures = 0;
>   
> -	tst_parse_opts(ac, av, NULL, NULL);
> -/*
> - * Tested on ppc64/x86_64/i386/s390x. And only 64bit has this issue.
> - * Since a 32bit program can't mmap so many memory.
> - */
> -#ifdef TST_ABI32
> -	tst_brkm(TCONF, NULL, "This test is only for 64bit.");
> -#endif
> -	setup();
> -	for (lc = 0; TEST_LOOPING(lc); lc++) {
> -		tst_count = 0;
> -
> -		reproduced = fork_test();
> -		if (reproduced == 0)
> -			tst_resm(TPASS, "fork failed as expected.");
> -	}
> -	cleanup();
> -	tst_exit();
> -}
> +	for (i = 0; i < EXTENT; i++) {
> +		mem = mmap(NULL, 1 * TST_GB,
> +			PROT_READ | PROT_WRITE,
> +			MAP_PRIVATE | MAP_ANONYMOUS,
> +			0, 0);
>   
> -static void setup(void)
> -{
> -	tst_sig(FORK, DEF_HANDLER, cleanup);
> -	TEST_PAUSE;
> +		if (mem == MAP_FAILED) {
> +			failures++;
>   
> -	pointer_vec = SAFE_MALLOC(cleanup, EXTENT * sizeof(char *));
> -}
> +			tst_res(TINFO, "mmap() failed");
>   
> -static void cleanup(void)
> -{
> -	free(pointer_vec);
> -}
> +			if (failures > 10) {
> +				tst_brk(TCONF, "mmap() fails too many "
> +					"times, so it's almost impossible to "
> +					"get a vm_area_struct sized 16TB.");
> +			}
>   
> -static int fork_test(void)
> -{
> -	int i, j, prev_failed = 0, fails = 0, cnt = 0;
> -	int reproduced = 0;
> -	void *addr;
> +			continue;
> +		}
>   
> -	for (i = 0; i < EXTENT; i++) {
> -		addr = mmap(NULL, 1 * GB, PROT_READ | PROT_WRITE,
> -			    MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
> -		if (addr == MAP_FAILED) {
> -			pointer_vec[i] = NULL;
> -			fails++;
> -			/*
> -			 * EXTENT is "16*1024+10", if fails count exceeds 10,
> -			 * we are almost impossible to get an vm_area_struct
> -			 * sized 16TB
> +		memvec[i] = mem;
> +
> +		pid = fork();
> +
> +		if (pid == -1) {
> +			/* keep track of the failed fork() and verify that next one
> +			 * is failing as well.
>   			 */
> -			if (fails == 11) {
> -				tst_brkm(TCONF, cleanup, "mmap() fails too many"
> -					 "times, so we are almost impossible to"
> -					 " get an vm_area_struct sized 16TB.");
> -			}
> -		} else {
> -			pointer_vec[i] = addr;
> +			prev_failed = 1;
> +			continue;
>   		}
> -		cnt++;
>   
> -		switch (tst_fork()) {
> -		case -1:
> -			prev_failed = 1;
> -		break;
> -		case 0:
> +		if (!pid)
>   			exit(0);
> -		default:
> -			SAFE_WAITPID(cleanup, -1, NULL, 0);
>   
> -			if (prev_failed > 0 && i >= LARGE) {
> -				tst_resm(TFAIL, "Fork succeeds incorrectly");
> -				reproduced = 1;
> -				goto clear_memory_map;
> -			}
> +		ret = waitpid(pid, NULL, 0);
> +		if (ret == -1 && errno != ECHILD)
> +			tst_brk(TBROK | TERRNO, "waitpid() error");
> +
> +		if (prev_failed && i >= LARGE) {
> +			passed = 0;
> +			break;
>   		}
> +
> +		prev_failed = 0;
> +
> +		tst_res(TINFO, "fork() passed at %d attempt", i);
>   	}
>   
> -clear_memory_map:
> -	for (j = 0; j < cnt; j++) {
> -		if (pointer_vec[j])
> -			SAFE_MUNMAP(cleanup, pointer_vec[j], 1 * GB);
> +	for (j = 0; j < i; j++) {
> +		if (memvec[j])
> +			SAFE_MUNMAP(memvec[j], 1 * TST_GB);

The memvec array never gets cleared after setup() so if you run the test 
with multiple iterations (e.g. -i 5), non-NULL pointers will accumulate 
in memvec between test iterations and you may end up unmapping an 
address range that was reused by libc.

>   	}
>   
> -	return reproduced;
> +	if (passed)
> +		tst_res(TPASS, "fork() failed as expected");
> +	else
> +		tst_res(TFAIL, "fork() succeeded incorrectly");
>   }
> +
> +static void setup(void)
> +{
> +	memvec = SAFE_MALLOC(EXTENT * sizeof(char *));
> +	memset(memvec, 0, EXTENT);
> +}
> +
> +static void cleanup(void)
> +{
> +	for (long i = 0; i < EXTENT; i++) {
> +		if (memvec && memvec[i])
> +			SAFE_MUNMAP(memvec[i], 1 * TST_GB);
> +	}
> +
> +	if (memvec)
> +		free(memvec);
> +}
> +
> +static struct tst_test test = {
> +	.test_all = run,
> +	.setup = setup,
> +	.cleanup = cleanup,
> +	.forks_child = 1,
> +	.skip_in_compat = 1,
> +	.tags = (const struct tst_tag[]) {
> +		{"linux-git", "7edc8b0ac16c"},
> +		{}
> +	}
> +};

-- 
Martin Doucha   mdoucha@suse.cz
SW Quality Engineer
SUSE LINUX, s.r.o.
CORSO IIa
Krizikova 148/34
186 00 Prague 8
Czech Republic


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Re: [LTP] [PATCH v5] Refactor fork14 using new LTP API

[Andrea Cervesato via ltp]

Hi Martin,

thanks for the review. I'm going to fix it

On 5/2/24 15:20, Martin Doucha wrote:
> Hi,
> there's a stale pointer issue in memvec if you run the test with 
> multiple iterations. See below.
>
> On 22. 03. 24 10:04, Andrea Cervesato wrote:
>> From: Andrea Cervesato <andrea.cervesato@suse.com>
>>
>> Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
>> ---
>> .skip_in_compat usage
>> Fixed typos
>> Fixed license
>>
>>   testcases/kernel/syscalls/fork/fork14.c | 205 +++++++++++-------------
>>   1 file changed, 92 insertions(+), 113 deletions(-)
>>
>> diff --git a/testcases/kernel/syscalls/fork/fork14.c 
>> b/testcases/kernel/syscalls/fork/fork14.c
>> index 93af2ebac..421f2caa3 100644
>> --- a/testcases/kernel/syscalls/fork/fork14.c
>> +++ b/testcases/kernel/syscalls/fork/fork14.c
>> @@ -1,143 +1,122 @@
>> -/*********************************************************************
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>>    * Copyright (C) 2014  Red Hat, Inc.
>> - *
>> - * This program is free software; you can redistribute it and/or
>> - * modify it under the terms of version 2 of the GNU General Public
>> - * License as published by the Free Software Foundation.
>> - *
>> - * This program is distributed in the hope that it would be useful,
>> - * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
>> - *
>> - * Further, this software is distributed without any warranty that it
>> - * is free of the rightful claim of any third person regarding
>> - * infringement or the like.  Any license provided herein, whether
>> - * implied or otherwise, applies only to this software file. Patent
>> - * licenses, if any, provided herein do not apply to combinations of
>> - * this program with other software, or any other product whatsoever.
>> - *
>> - * You should have received a copy of the GNU General Public License
>> - * along with this program; if not, write the Free Software
>> - * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
>> - * 02110-1301, USA.
>> + * Copyright (C) 2023 SUSE LLC Andrea Cervesato 
>> <andrea.cervesato@suse.com>
>> + */
>> +
>> +/*\
>> + * [Description]
>>    *
>>    * This test is a reporducer for this patch:
>> - *              https://lkml.org/lkml/2012/4/24/328
>> + * 
>> https://lore.kernel.org/lkml/1335289853-2923-1-git-send-email-siddhesh.poyarekar@gmail.com/
>>    * Since vma length in dup_mmap is calculated and stored in a unsigned
>>    * int, it will overflow when length of mmaped memory > 16 TB. When
>> - * overflow occur, fork will  incorrectly succeed. The patch above
>> - * fixed it.
>> - ********************************************************************/
>> + * overflow occurs, fork will incorrectly succeed. The patch above 
>> fixed it.
>> + */
>>   -#include <sys/mman.h>
>> +#include "tst_test.h"
>> +#include <stdlib.h>
>>   #include <sys/wait.h>
>> -#include <stdio.h>
>> -#include <unistd.h>
>> -#include "test.h"
>> -#include "safe_macros.h"
>> -#include "lapi/abisize.h"
>> -
>> -char *TCID = "fork14";
>> -int TST_TOTAL = 1;
>>   -#define GB        (1024 * 1024 * 1024L)
>> -
>> -/* set mmap threshold to 16TB */
>>   #define LARGE        (16 * 1024)
>>   #define EXTENT        (16 * 1024 + 10)
>>   -static char **pointer_vec;
>> -
>> -static void setup(void);
>> -static void cleanup(void);
>> -static int  fork_test(void);
>> +static char **memvec;
>>   -int main(int ac, char **av)
>> +static void run(void)
>>   {
>> -    int lc, reproduced;
>> +    int i, j, ret;
>> +    pid_t pid;
>> +    void *mem;
>> +    int prev_failed = 0;
>> +    int passed = 1;
>> +    int failures = 0;
>>   -    tst_parse_opts(ac, av, NULL, NULL);
>> -/*
>> - * Tested on ppc64/x86_64/i386/s390x. And only 64bit has this issue.
>> - * Since a 32bit program can't mmap so many memory.
>> - */
>> -#ifdef TST_ABI32
>> -    tst_brkm(TCONF, NULL, "This test is only for 64bit.");
>> -#endif
>> -    setup();
>> -    for (lc = 0; TEST_LOOPING(lc); lc++) {
>> -        tst_count = 0;
>> -
>> -        reproduced = fork_test();
>> -        if (reproduced == 0)
>> -            tst_resm(TPASS, "fork failed as expected.");
>> -    }
>> -    cleanup();
>> -    tst_exit();
>> -}
>> +    for (i = 0; i < EXTENT; i++) {
>> +        mem = mmap(NULL, 1 * TST_GB,
>> +            PROT_READ | PROT_WRITE,
>> +            MAP_PRIVATE | MAP_ANONYMOUS,
>> +            0, 0);
>>   -static void setup(void)
>> -{
>> -    tst_sig(FORK, DEF_HANDLER, cleanup);
>> -    TEST_PAUSE;
>> +        if (mem == MAP_FAILED) {
>> +            failures++;
>>   -    pointer_vec = SAFE_MALLOC(cleanup, EXTENT * sizeof(char *));
>> -}
>> +            tst_res(TINFO, "mmap() failed");
>>   -static void cleanup(void)
>> -{
>> -    free(pointer_vec);
>> -}
>> +            if (failures > 10) {
>> +                tst_brk(TCONF, "mmap() fails too many "
>> +                    "times, so it's almost impossible to "
>> +                    "get a vm_area_struct sized 16TB.");
>> +            }
>>   -static int fork_test(void)
>> -{
>> -    int i, j, prev_failed = 0, fails = 0, cnt = 0;
>> -    int reproduced = 0;
>> -    void *addr;
>> +            continue;
>> +        }
>>   -    for (i = 0; i < EXTENT; i++) {
>> -        addr = mmap(NULL, 1 * GB, PROT_READ | PROT_WRITE,
>> -                MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
>> -        if (addr == MAP_FAILED) {
>> -            pointer_vec[i] = NULL;
>> -            fails++;
>> -            /*
>> -             * EXTENT is "16*1024+10", if fails count exceeds 10,
>> -             * we are almost impossible to get an vm_area_struct
>> -             * sized 16TB
>> +        memvec[i] = mem;
>> +
>> +        pid = fork();
>> +
>> +        if (pid == -1) {
>> +            /* keep track of the failed fork() and verify that next one
>> +             * is failing as well.
>>                */
>> -            if (fails == 11) {
>> -                tst_brkm(TCONF, cleanup, "mmap() fails too many"
>> -                     "times, so we are almost impossible to"
>> -                     " get an vm_area_struct sized 16TB.");
>> -            }
>> -        } else {
>> -            pointer_vec[i] = addr;
>> +            prev_failed = 1;
>> +            continue;
>>           }
>> -        cnt++;
>>   -        switch (tst_fork()) {
>> -        case -1:
>> -            prev_failed = 1;
>> -        break;
>> -        case 0:
>> +        if (!pid)
>>               exit(0);
>> -        default:
>> -            SAFE_WAITPID(cleanup, -1, NULL, 0);
>>   -            if (prev_failed > 0 && i >= LARGE) {
>> -                tst_resm(TFAIL, "Fork succeeds incorrectly");
>> -                reproduced = 1;
>> -                goto clear_memory_map;
>> -            }
>> +        ret = waitpid(pid, NULL, 0);
>> +        if (ret == -1 && errno != ECHILD)
>> +            tst_brk(TBROK | TERRNO, "waitpid() error");
>> +
>> +        if (prev_failed && i >= LARGE) {
>> +            passed = 0;
>> +            break;
>>           }
>> +
>> +        prev_failed = 0;
>> +
>> +        tst_res(TINFO, "fork() passed at %d attempt", i);
>>       }
>>   -clear_memory_map:
>> -    for (j = 0; j < cnt; j++) {
>> -        if (pointer_vec[j])
>> -            SAFE_MUNMAP(cleanup, pointer_vec[j], 1 * GB);
>> +    for (j = 0; j < i; j++) {
>> +        if (memvec[j])
>> +            SAFE_MUNMAP(memvec[j], 1 * TST_GB);
>
> The memvec array never gets cleared after setup() so if you run the 
> test with multiple iterations (e.g. -i 5), non-NULL pointers will 
> accumulate in memvec between test iterations and you may end up 
> unmapping an address range that was reused by libc.
>
>>       }
>>   -    return reproduced;
>> +    if (passed)
>> +        tst_res(TPASS, "fork() failed as expected");
>> +    else
>> +        tst_res(TFAIL, "fork() succeeded incorrectly");
>>   }
>> +
>> +static void setup(void)
>> +{
>> +    memvec = SAFE_MALLOC(EXTENT * sizeof(char *));
>> +    memset(memvec, 0, EXTENT);
>> +}
>> +
>> +static void cleanup(void)
>> +{
>> +    for (long i = 0; i < EXTENT; i++) {
>> +        if (memvec && memvec[i])
>> +            SAFE_MUNMAP(memvec[i], 1 * TST_GB);
>> +    }
>> +
>> +    if (memvec)
>> +        free(memvec);
>> +}
>> +
>> +static struct tst_test test = {
>> +    .test_all = run,
>> +    .setup = setup,
>> +    .cleanup = cleanup,
>> +    .forks_child = 1,
>> +    .skip_in_compat = 1,
>> +    .tags = (const struct tst_tag[]) {
>> +        {"linux-git", "7edc8b0ac16c"},
>> +        {}
>> +    }
>> +};
>
Andrea


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