Messages in this thread | | | Subject | Re: [PATCH v3] kernel/module: Fix mem leak in module_add_modinfo_attrs | From | Yuehaibing <> | Date | Tue, 4 Jun 2019 21:54:44 +0800 |
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On 2019/6/4 18:46, Miroslav Benes wrote: > On Mon, 3 Jun 2019, YueHaibing wrote: > >> In module_add_modinfo_attrs if sysfs_create_file >> fails, we forget to free allocated modinfo_attrs >> and roll back the sysfs files. >> >> Fixes: 03e88ae1b13d ("[PATCH] fix module sysfs files reference counting") >> Signed-off-by: YueHaibing <yuehaibing@huawei.com> >> --- >> v3: reuse module_remove_modinfo_attrs >> v2: free from '--i' instead of 'i--' >> --- >> kernel/module.c | 21 ++++++++++++++++----- >> 1 file changed, 16 insertions(+), 5 deletions(-) > > I'm afraid it is not completely correct. > >> diff --git a/kernel/module.c b/kernel/module.c >> index 80c7c09..c6b8912 100644 >> --- a/kernel/module.c >> +++ b/kernel/module.c >> @@ -1697,6 +1697,8 @@ static int add_usage_links(struct module *mod) >> return ret; >> } >> >> +static void module_remove_modinfo_attrs(struct module *mod, int end); >> + >> static int module_add_modinfo_attrs(struct module *mod) >> { >> struct module_attribute *attr; >> @@ -1711,24 +1713,33 @@ static int module_add_modinfo_attrs(struct module *mod) >> return -ENOMEM; >> >> temp_attr = mod->modinfo_attrs; >> - for (i = 0; (attr = modinfo_attrs[i]) && !error; i++) { >> + for (i = 0; (attr = modinfo_attrs[i]); i++) { >> if (!attr->test || attr->test(mod)) { >> memcpy(temp_attr, attr, sizeof(*temp_attr)); >> sysfs_attr_init(&temp_attr->attr); >> error = sysfs_create_file(&mod->mkobj.kobj, >> &temp_attr->attr); >> + if (error) >> + goto error_out; > > sysfs_create_file() failed, so we need to clear all previously processed > attrs and not the current one. > >> ++temp_attr; >> } >> } >> + >> + return 0; >> + >> +error_out: >> + module_remove_modinfo_attrs(mod, --i); > > It says "call sysfs_remove_file() on all attrs ending with --i included > (all correctly processed attrs). > >> return error; >> } >> >> -static void module_remove_modinfo_attrs(struct module *mod) >> +static void module_remove_modinfo_attrs(struct module *mod, int end) >> { >> struct module_attribute *attr; >> int i; >> >> for (i = 0; (attr = &mod->modinfo_attrs[i]); i++) { >> + if (end >= 0 && i > end) >> + break; > > If end == 0, you break the loop without calling sysfs_remove_file(), which > is a bug if you called module_remove_modinfo_attrs(mod, 0).
If end == 0 and i == 0, if statement is false, it won't break the loop.
At other places, I use end == -1, which means clean all and keeps the old behavior
- module_remove_modinfo_attrs(mod); + module_remove_modinfo_attrs(mod, -1);
> > Calling module_remove_modinfo_attrs(mod, i); in module_add_modinfo_attrs() > under error_out label and changing the condition here to > > if (end >= 0 && i >= end) > break; > > should work as expected. > > But let me ask another question and it might be more to Jessica. Why is > there even a call to attr->free(mod); (if it exists) in > module_remove_modinfo_attrs()? The same is in free_modinfo() (as opposed > to setup_modinfo() where attr->setup(mod) is called. Is it because > free_modinfo() is called only in load_module()'s error path, while > module_remove_modinfo_attrs() is called even in free_module() path? > > kfree() checks for NULL pointer, so there is no bug, but it is certainly > not nice and it calls for cleanup. But I may be missing something. > > Regards, > Miroslav > > . >
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