linux-kernel - [PATCH 01/15] modpost: remove incorrect code in do_eisa

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Message-ID: <20241119235705.1576946-1-masahiroy@kernel.org>
Date: Wed, 20 Nov 2024 08:56:39 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: linux-kbuild@...r.kernel.org
Cc: Masahiro Yamada <masahiroy@...nel.org>,
	Andreas Schwab <schwab@...ux-m68k.org>,
	Jean Delvare <khali@...ux-fr.org>,
	Jochen Friedrich <jochen@...am.de>,
	Michal Marek <mmarek@...e.cz>,
	Nathan Chancellor <nathan@...nel.org>,
	Nicolas Schier <nicolas@...sle.eu>,
	Sam Ravnborg <sam@...nborg.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 01/15] modpost: remove incorrect code in do_eisa_entry()

This function contains multiple bugs after the following commits:

 - ac551828993e ("modpost: i2c aliases need no trailing wildcard")
 - 6543becf26ff ("mod/file2alias: make modalias generation safe for cross compiling")

Commit ac551828993e inserted the following code to do_eisa_entry():

    else
            strcat(alias, "*");

This is incorrect because 'alias' is uninitialized. If it is not
NULL-terminated, strcat() could cause a buffer overrun.

Even if 'alias' happens to be zero-filled, it would output:

    MODULE_ALIAS("*");

This would match anything. As a result, the module could be loaded by
any unrelated uevent from an unrelated subsystem.

Commit ac551828993e introduced another bug.            

Prior to that commit, the conditional check was:

    if (eisa->sig[0])

This checked if the first character of eisa_device_id::sig was not '\0'.

However, commit ac551828993e changed it as follows:

    if (sig[0])

sig[0] is NOT the first character of the eisa_device_id::sig. The
type of 'sig' is 'char (*)[8]', meaning that the type of 'sig[0]' is
'char [8]' instead of 'char'. 'sig[0]' and 'symval' refer to the same
address, which never becomes NULL.

The correct conversion would have been:

    if ((*sig)[0])

However, this if-conditional was meaningless because the earlier change
in commit ac551828993e was incorrect.

This commit removes the entire incorrect code, which should never have
been executed.

Fixes: ac551828993e ("modpost: i2c aliases need no trailing wildcard")
Fixes: 6543becf26ff ("mod/file2alias: make modalias generation safe for cross compiling")
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---

 scripts/mod/file2alias.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
index c4cc11aa558f..634e40748287 100644
--- a/scripts/mod/file2alias.c
+++ b/scripts/mod/file2alias.c
@@ -809,10 +809,7 @@ static int do_eisa_entry(const char *filename, void *symval,
 		char *alias)
 {
 	DEF_FIELD_ADDR(symval, eisa_device_id, sig);
-	if (sig[0])
-		sprintf(alias, EISA_DEVICE_MODALIAS_FMT "*", *sig);
-	else
-		strcat(alias, "*");
+	sprintf(alias, EISA_DEVICE_MODALIAS_FMT "*", *sig);
 	return 1;
 }

-- 
2.43.0