linux-kernel - [PATCH] init/initramfs: Fix argument forwarding to panic() in panic_show

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Message-Id: <20230320230534.50174-1-bgray@linux.ibm.com>
Date:   Tue, 21 Mar 2023 10:05:34 +1100
From:   Benjamin Gray <bgray@...ux.ibm.com>
To:     linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org
Cc:     Benjamin Gray <bgray@...ux.ibm.com>
Subject: [PATCH] init/initramfs: Fix argument forwarding to panic() in panic_show_mem()

Forwarding variadic argument lists can't be done by passing a va_list
to a function with signature foo(...) (as panic() has). It ends up
interpreting the va_list itself as a single argument instead of
iterating it. printf() happily accepts it of course, leading to corrupt
output.

Convert panic_show_mem() to a macro to allow forwarding the arguments.
The function is trivial enough that it's easier than trying to introduce
a vpanic() variant.

Signed-off-by: Benjamin Gray <bgray@...ux.ibm.com>

---

After sending these patches [1] I wondered why the kernel accepted a
corrupt archive. The streaming parser makes it difficult to see
where to add a completeness check (possibly can assert the state is
Start or Reset at the end?), but adding an error() to cover my issue
revealed that the error message was never printed.

[1]: https://lore.kernel.org/all/20230320040839.660475-1-bgray@linux.ibm.com/
---
 init/initramfs.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/init/initramfs.c b/init/initramfs.c
index f6c112e30bd4..e7a01c2ccd1b 100644
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -60,15 +60,8 @@ static void __init error(char *x)
 		message = x;
 }

-static void panic_show_mem(const char *fmt, ...)
-{
-	va_list args;
-
-	show_mem(0, NULL);
-	va_start(args, fmt);
-	panic(fmt, args);
-	va_end(args);
-}
+#define panic_show_mem(fmt, ...) \
+	({ show_mem(0, NULL); panic(fmt, ##__VA_ARGS__); })

 /* link hash */

base-commit: 065ffaee73892e8a3629b4cfbe635697807a3c6f
prerequisite-patch-id: 6e3cfc6bf9c5686ad29c7feed8e283d30b1957fd
prerequisite-patch-id: 933a7bd2f29223dba7f2cac7e9aa72aae730292d
-- 
2.39.2