[LTP] [PATCH] listmount04: Detect EBADF behavior dynamically at runtime

[LTP] [PATCH] listmount04: Detect EBADF behavior dynamically at runtime

[Wake Liu via ltp]

Upstream commit 78f0e33cd6c9 ("fs/namespace: correctly handle errors
returned by grab_requested_mnt_ns") changed the errno from EINVAL to
EBADF when an invalid mount namespace file descriptor is passed to
listmount(). This change has been backported to various stable kernels
(e.g., 6.12.59 LTS).

Instead of hardcoding version checks for every stable backport, probe
the behavior dynamically in setup() by calling listmount() with an
invalid fd (-1) and checking the returned errno.

Signed-off-by: Wake Liu <wakel@google.com>
---
 .../kernel/syscalls/listmount/listmount04.c   | 27 ++++++++++++++++---
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/testcases/kernel/syscalls/listmount/listmount04.c b/testcases/kernel/syscalls/listmount/listmount04.c
index 919f4c854..f7343608f 100644
--- a/testcases/kernel/syscalls/listmount/listmount04.c
+++ b/testcases/kernel/syscalls/listmount/listmount04.c
@@ -153,16 +153,35 @@ static void run(unsigned int n)
 	}
 
 	TST_EXP_FAIL(tst_syscall(__NR_listmount, req, tc->mnt_ids,
-		tc->nr_mnt_ids, tc->flags), tc->exp_errno,
-		"%s", tc->msg);
+				 tc->nr_mnt_ids, tc->flags),
+		     tc->exp_errno,
+		     "%s", tc->msg);
 }
 
 static void setup(void)
 {
-	if (tst_kvercmp(6, 17, 9) >= 0)
+	mnt_id_req req = {
+		.size = MNT_ID_REQ_SIZE_VER0,
+		.mnt_id = LSMT_ROOT,
+		.mnt_ns_fd = -1,
+	};
+	uint64_t ids[MNT_SIZE];
+
+	TEST(tst_syscall(__NR_listmount, &req, ids, MNT_SIZE, 0));
+	if (TST_RET >= 0)
+		tst_brk(TBROK, "listmount() succeeded unexpectedly with invalid fd");
+
+	if (TST_ERR == EBADF) {
 		kver = AFTER_6_17_9;
-	else
+		tst_res(TINFO, "Detected kernel with EBADF behavior for invalid mnt_ns_fd");
+	} else if (TST_ERR == EINVAL) {
 		kver = BEFORE_6_17_9;
+		tst_res(TINFO, "Detected kernel with EINVAL behavior for invalid mnt_ns_fd");
+	} else if (TST_ERR == ENOSYS) {
+		tst_brk(TCONF, "listmount() syscall not supported");
+	} else {
+		tst_brk(TBROK | TTERRNO, "Unexpected error during probe");
+	}
 }
 
 static struct tst_test test = {
-- 
2.55.0.487.gaf234c4eb3-goog


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Re: [LTP] [PATCH] listmount04: Detect EBADF behavior dynamically at runtime

[Petr Vorel]

> Upstream commit 78f0e33cd6c9 ("fs/namespace: correctly handle errors
> returned by grab_requested_mnt_ns") changed the errno from EINVAL to
> EBADF when an invalid mount namespace file descriptor is passed to
> listmount(). This change has been backported to various stable kernels
> (e.g., 6.12.59 LTS).

> Instead of hardcoding version checks for every stable backport, probe
> the behavior dynamically in setup() by calling listmount() with an
> invalid fd (-1) and checking the returned errno.

> Signed-off-by: Wake Liu <wakel@google.com>
> ---
>  .../kernel/syscalls/listmount/listmount04.c   | 27 ++++++++++++++++---
>  1 file changed, 23 insertions(+), 4 deletions(-)

> diff --git a/testcases/kernel/syscalls/listmount/listmount04.c b/testcases/kernel/syscalls/listmount/listmount04.c
> index 919f4c854..f7343608f 100644
> --- a/testcases/kernel/syscalls/listmount/listmount04.c
> +++ b/testcases/kernel/syscalls/listmount/listmount04.c
> @@ -153,16 +153,35 @@ static void run(unsigned int n)
>  	}

>  	TST_EXP_FAIL(tst_syscall(__NR_listmount, req, tc->mnt_ids,
> -		tc->nr_mnt_ids, tc->flags), tc->exp_errno,
> -		"%s", tc->msg);
> +				 tc->nr_mnt_ids, tc->flags),
> +		     tc->exp_errno,
> +		     "%s", tc->msg);
>  }

>  static void setup(void)
>  {
> -	if (tst_kvercmp(6, 17, 9) >= 0)
> +	mnt_id_req req = {
> +		.size = MNT_ID_REQ_SIZE_VER0,
> +		.mnt_id = LSMT_ROOT,
> +		.mnt_ns_fd = -1,
> +	};
> +	uint64_t ids[MNT_SIZE];
> +
> +	TEST(tst_syscall(__NR_listmount, &req, ids, MNT_SIZE, 0));
I wonder if we should use listmount() from listmount.h.

> +	if (TST_RET >= 0)
> +		tst_brk(TBROK, "listmount() succeeded unexpectedly with invalid fd");
Maybe we could have TST_EXP_FAIL_ARR_SILENT_BRK() in the future :)

> +
> +	if (TST_ERR == EBADF) {
>  		kver = AFTER_6_17_9;
At this point we may rename macros back to AFTER_6_18 and BEFORE_6_18, with
keeping note that it got backported into stable.

> -	else
> +		tst_res(TINFO, "Detected kernel with EBADF behavior for invalid mnt_ns_fd");
> +	} else if (TST_ERR == EINVAL) {
>  		kver = BEFORE_6_17_9;
> +		tst_res(TINFO, "Detected kernel with EINVAL behavior for invalid mnt_ns_fd");
> +	} else if (TST_ERR == ENOSYS) {
> +		tst_brk(TCONF, "listmount() syscall not supported");
This is IMHO not supported, because it's part of tst_syscall().
Other than this LGTM.
Reviewed-by: Petr Vorel <pvorel@suse.cz>

Kind regards,
Petr

> +	} else {
> +		tst_brk(TBROK | TTERRNO, "Unexpected error during probe");
> +	}

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