+++ 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 <[email protected]> Signed-off-by: Xie XiuQi <[email protected]> --- 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
