[LTP] [PATCH v3 0/2] shmctl03: Fix shmmax clamped to INT_MAX in 32bit compat mode

[LTP] [PATCH v3 0/2] shmctl03: Fix shmmax clamped to INT_MAX in 32bit compat mode

[Petr Vorel]

Changes v2->v3:
* Drop first fix from Andrea:
  https://lore.kernel.org/ltp/20260924112514.2375626-2-pvorel@suse.cz/
  I'm no longer confident it's a good idea even if we document changed
  behavior. See my concern:
  https://lore.kernel.org/ltp/20260925080154.GC2387785@pevik/
  Maybe we should either handle this entirely in shmctl03.c as there is
  no other test which needs it.
* Use unsigned long instead of unsigned long long (no need for that big
  variable)
* Use correct macro TST_EXP_EQ_LU() (agent)
* Read shmmax only once (agent)
* TST_EXP_POSITIVE SAFE_SHMCTL() instead of safe_shmctl() (no TBROK
  instead of TFAIL in case of failure and it's probably slightly more
  readable)

Petr Vorel (2):
  shmctl03: Fix shmmax clamped to INT_MAX in 32bit compat mode
  shmctl03: Use test macros

 testcases/kernel/syscalls/shmctl/shmctl03.c | 24 ++++++++++-----------
 1 file changed, 12 insertions(+), 12 deletions(-)

-- 
2.55.0


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[LTP] [PATCH v3 1/2] shmctl03: Fix shmmax clamped to INT_MAX in 32bit compat mode

[Petr Vorel]

Kernel clamped shmmax returned from shmctl(IPC_INFO) in 32bit compat
mode to INT_MAX due to a change in kernel v2.6.22 in commit
af7c693f14606 ("Cap shmmax at INT_MAX in compat shminfo").
Reflect that.

This fixes error:

    shmctl03.c:33: TFAIL: /proc/sys/kernel/shmmax != 2147483647 got 4294967295

Reported-by: Wei Gao <wegao@suse.com>
Suggested-by: Andrea Cervesato <andrea.cervesato@suse.com>
Signed-off-by: Petr Vorel <pvorel@suse.cz>
---
 testcases/kernel/syscalls/shmctl/shmctl03.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/testcases/kernel/syscalls/shmctl/shmctl03.c b/testcases/kernel/syscalls/shmctl/shmctl03.c
index 9e1c2f0990..f2b735dc85 100644
--- a/testcases/kernel/syscalls/shmctl/shmctl03.c
+++ b/testcases/kernel/syscalls/shmctl/shmctl03.c
@@ -16,6 +16,7 @@
 static void verify_ipcinfo(void)
 {
 	struct shminfo info;
+	unsigned long shmmax;
 
 	TEST(shmctl(0, IPC_INFO, (struct shmid_ds *)&info));
 
@@ -30,7 +31,12 @@ static void verify_ipcinfo(void)
 	else
 		tst_res(TPASS, "shmmin = 1");
 
-	TST_ASSERT_ULONG(PATH_KERN_SHMMAX, info.shmmax);
+	SAFE_FILE_SCANF(PATH_KERN_SHMMAX, "%lu", &shmmax);
+	if (tst_is_compat_mode() && info.shmmax == INT_MAX)
+		TST_EXP_LE_LU(INT_MAX, shmmax);
+	else
+		TST_EXP_EQ_LU(info.shmmax, shmmax);
+
 	TST_ASSERT_ULONG(PATH_KERN_SHMMNI, info.shmmni);
 	TST_ASSERT_ULONG(PATH_KERN_SHMALL, info.shmall);
 }
-- 
2.55.0


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[LTP] [PATCH v3 2/2] shmctl03: Use test macros

[Petr Vorel]

Use test macros to shorten the code.
Link manpage.

Signed-off-by: Petr Vorel <pvorel@suse.cz>
---
 testcases/kernel/syscalls/shmctl/shmctl03.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/testcases/kernel/syscalls/shmctl/shmctl03.c b/testcases/kernel/syscalls/shmctl/shmctl03.c
index f2b735dc85..bccab5ba37 100644
--- a/testcases/kernel/syscalls/shmctl/shmctl03.c
+++ b/testcases/kernel/syscalls/shmctl/shmctl03.c
@@ -1,11 +1,12 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Copyright (C) 2020 Cyril Hrubis <chrubis@suse.cz>
+ * Copyright (c) Linux Test Project, 2026
  */
 
 /*\
- * Call shmctl() with IPC_INFO flag and check that the data are consistent with
- * /proc/sys/kernel/shm*.
+ * Call :manpage:`shmctl(2)` with IPC_INFO flag and check that the data are
+ * consistent with /proc/sys/kernel/shm*.
  */
 
 #define _GNU_SOURCE
@@ -18,18 +19,11 @@ static void verify_ipcinfo(void)
 	struct shminfo info;
 	unsigned long shmmax;
 
-	TEST(shmctl(0, IPC_INFO, (struct shmid_ds *)&info));
-
-	if (TST_RET < 0) {
-		tst_res(TFAIL | TTERRNO,
-			"shmctl(0, IPC_INFO, ...) returned %li", TST_RET);
+	TST_EXP_POSITIVE(shmctl(0, IPC_INFO, (struct shmid_ds *)&info));
+	if (!TST_PASS)
 		return;
-	}
 
-	if (info.shmmin != 1)
-		tst_res(TFAIL, "shmmin = %li, expected 1", info.shmmin);
-	else
-		tst_res(TPASS, "shmmin = 1");
+	TST_EXP_EQ_LU(info.shmmin, 1);
 
 	SAFE_FILE_SCANF(PATH_KERN_SHMMAX, "%lu", &shmmax);
 	if (tst_is_compat_mode() && info.shmmax == INT_MAX)
-- 
2.55.0


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Re: [LTP] shmctl03: Fix shmmax clamped to INT_MAX in 32bit compat mode

[linuxtestproject.agent]

Hi Petr,

On Fri, 25 Sep 2026 10:28:39 +0200, Petr Vorel wrote:
> [PATCH 1/2] shmctl03: Fix shmmax clamped to INT_MAX in 32bit compat mode

--- [PATCH 1/2] ---

> +	SAFE_FILE_SCANF(PATH_KERN_SHMMAX, "%lu", &shmmax);
> +	if (tst_is_compat_mode() && info.shmmax == INT_MAX)
> +		TST_EXP_LE_LU(INT_MAX, shmmax);
> +	else
> +		TST_EXP_EQ_LU(info.shmmax, shmmax);

Testing `info.shmmax == INT_MAX` in the condition masks regressions; if the
kernel fails to clamp `info.shmmax`, execution takes the else branch and
reports TPASS. Additionally, `TST_EXP_LE_LU(INT_MAX, shmmax)` compares
`INT_MAX` against `shmmax` rather than verifying `info.shmmax`. Use
`unsigned long long` with `"%llu"` to avoid 32-bit overflow when reading
`PATH_KERN_SHMMAX`, and assert `info.shmmax` equals `INT_MAX` when
`tst_is_compat_mode() && shmmax > INT_MAX` (or `shmmax` otherwise).

Verdict - Needs revision

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