linux-kernel - [PATCH v2 2/3] coredump: fix error handling for replace

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Message-Id: <20250414-work-coredump-v2-2-685bf231f828@kernel.org>
Date: Mon, 14 Apr 2025 15:55:06 +0200
From: Christian Brauner <brauner@...nel.org>
To: linux-fsdevel@...r.kernel.org
Cc: Oleg Nesterov <oleg@...hat.com>, 
 Luca Boccassi <luca.boccassi@...il.com>, 
 Lennart Poettering <lennart@...ttering.net>, 
 Daan De Meyer <daan.j.demeyer@...il.com>, Mike Yuan <me@...dnzj.com>, 
 Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>, 
 linux-kernel@...r.kernel.org, Christian Brauner <brauner@...nel.org>
Subject: [PATCH v2 2/3] coredump: fix error handling for replace_fd()

The replace_fd() helper returns the file descriptor number on success
and a negative error code on failure. The current error handling in
umh_pipe_setup() only works because the file descriptor that is replaced
is zero but that's pretty volatile. Explicitly check for a negative
error code.

Tested-by: Luca Boccassi <luca.boccassi@...il.com>
Signed-off-by: Christian Brauner <brauner@...nel.org>
---
 fs/coredump.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/coredump.c b/fs/coredump.c
index c33c177a701b..9da592aa8f16 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -507,7 +507,9 @@ static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
 {
 	struct file *files[2];
 	struct coredump_params *cp = (struct coredump_params *)info->data;
-	int err = create_pipe_files(files, 0);
+	int err;
+
+	err = create_pipe_files(files, 0);
 	if (err)
 		return err;
 
@@ -515,10 +517,13 @@ static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
 
 	err = replace_fd(0, files[0], 0);
 	fput(files[0]);
+	if (err < 0)
+		return err;
+
 	/* and disallow core files too */
 	current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
 
-	return err;
+	return 0;
 }
 
 void do_coredump(const kernel_siginfo_t *siginfo)

-- 
2.47.2