linux-kernel - [PATCH] module: fix failed to rmmod kernel module when it's name is too long

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Date:   Fri, 13 Jan 2017 17:19:03 +0800
From:   Xie XiuQi <xiexiuqi@...wei.com>
To:     <jeyu@...hat.com>, <rusty@...tcorp.com.au>
CC:     <linux-kernel@...r.kernel.org>, <zhangliguang@...wei.com>
Subject: [PATCH] module: fix failed to rmmod kernel module when it's name is too long

When the name of kernel module is more than 56 chars (include 56),
the module could be insmod successfully, but failed to rmmod.

$ strace rmmod tst_1111111111222222222233333333334444444444555555555566
...
open("/sys/module/tst_1111111111222222222233333333334444444444555555555566/initstate", O_RDONLY|O_CLOEXEC) = 3
read(3, "live\n", 31)                   = 5
read(3, "", 26)                         = 0
close(3)                                = 0
openat(AT_FDCWD, "/sys/module/tst_1111111111222222222233333333334444444444555555555566/holders", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3
getdents(3, /* 2 entries */, 32768)     = 48
getdents(3, /* 0 entries */, 32768)     = 0
close(3)                                = 0
open("/sys/module/tst_1111111111222222222233333333334444444444555555555566/refcnt", O_RDONLY|O_CLOEXEC) = 3
read(3, "0\n", 31)                      = 2
read(3, "", 29)                         = 0
close(3)                                = 0
delete_module("tst_1111111111222222222233333333334444444444555555555566", O_RDONLY|O_NONBLOCK) = -1 ENOENT (No such file or directory)
write(2, "rmmod: ERROR: could not remove '"..., 117rmmod: ERROR: could not remove 'tst_1111111111222222222233333333334444444444555555555566': No such file or directory
) = 117
write(2, "rmmod: ERROR: could not remove m"..., 122rmmod: ERROR: could not remove module tst_1111111111222222222233333333334444444444555555555566: No such file or directory
) = 122
exit_group(1)                           = ?
+++ exited with 1 +++

In this patch, we just set the last char to '\0', to make sure
the name has the tailing '\0'.

Reported-by: Zhang Liguang <zhangliguang@...wei.com>
Signed-off-by: Xie XiuQi <xiexiuqi@...wei.com>
---
 kernel/module.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/module.c b/kernel/module.c
index 0e54d5b..3eac266 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2928,6 +2928,7 @@ static struct module *setup_load_info(struct load_info *info, int flags)
 	}
 	/* This is temporary: point mod into copy of data. */
 	mod = (void *)info->sechdrs[info->index.mod].sh_addr;
+	mod->name[MODULE_NAME_LEN - 1] = '\0';
 
 	if (info->index.sym == 0) {
 		pr_warn("%s: module has no symbols (stripped?)\n", mod->name);
-- 
1.8.3.1