* [PATCH] module: fix failed to rmmod kernel module when it's name is too long
@ 2017-01-13 9:19 Xie XiuQi
2017-01-19 3:26 ` Jessica Yu
0 siblings, 1 reply; 2+ messages in thread
From: Xie XiuQi @ 2017-01-13 9:19 UTC (permalink / raw)
To: jeyu, rusty; +Cc: linux-kernel, zhangliguang
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@huawei.com>
Signed-off-by: Xie XiuQi <xiexiuqi@huawei.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
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: module: fix failed to rmmod kernel module when it's name is too long
2017-01-13 9:19 [PATCH] module: fix failed to rmmod kernel module when it's name is too long Xie XiuQi
@ 2017-01-19 3:26 ` Jessica Yu
0 siblings, 0 replies; 2+ messages in thread
From: Jessica Yu @ 2017-01-19 3:26 UTC (permalink / raw)
To: Xie XiuQi; +Cc: rusty, linux-kernel, zhangliguang
+++ Xie XiuQi [13/01/17 17:19 +0800]:
>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@huawei.com>
>Signed-off-by: Xie XiuQi <xiexiuqi@huawei.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';
Does the patch actually fix the rmmod issue you're describing?
I tested it and rmmod still had issues finding the module because userspace
doesn't know its in-kernel name got truncated by one character. So kmod (rmmod)
would look for
/sys/module/tst_1111111111222222222233333333334444444444555555555566/initstate
instead of
/sys/module/tst_111111111122222222223333333333444444444455555555556/initstate
and subsequently fail with "module not loaded"
So, unfortunately this patch probably isn't enough fix this problem. When a
module's name is >= MODULE_NAME_LEN, it gets silently truncated in-kernel on
module load. Moreover, (1) userspace won't know about that happening and (2) the
module name found in .gnu.linkonce.this_module would also diverge from its name
in-kernel.
What might be nice to have is to have a compile-time assertion that breaks the
build if KBUILD_MODNAME exceeds MODULE_NAME_LEN, that way the error is clearly
user-visible, and we won't run into this problem in the first place. Plus
problems 1 and 2 mentioned above go away. Maybe we can have modpost insert a
BUILD_BUG_ON when KBUILD_MODNAME > MODULE_NAME_LEN?
Jessica
^ permalink raw reply [flat|nested] 2+ messages in thread
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2017-01-19 3:26 ` Jessica Yu
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