Re: Re: [BUG] fs/notify/mark: A potential use after free in fsnotify_put_mark_wake
> -原始邮件- > 发件人: "Jan Kara" > 发送时间: 2021-03-29 21:57:40 (星期一) > 收件人: lyl2...@mail.ustc.edu.cn > 抄送: j...@suse.cz, amir7...@gmail.com, linux-fsde...@vger.kernel.org, > linux-kernel@vger.kernel.org > 主题: Re: [BUG] fs/notify/mark: A potential use after free in > fsnotify_put_mark_wake > > Hello! > > > On Sun 28-03-21 17:11:43, lyl2...@mail.ustc.edu.cn wrote: > > My static analyzer tool reported a use after free in > > fsnotify_put_mark_wake > > of the file: fs/notify/mark.c. > > > > In fsnotify_put_mark_wake, it calls fsnotify_put_mark(mark). Inside the > > function > > fsnotify_put_mark(), if conn is NULL, it will call > > fsnotify_final_mark_destroy(mark) > > to free mark->group by fsnotify_put_group(group) and return. I also had > > inspected > > the implementation of fsnotify_put_group() and found that there is no > > cleanup operation > > about group->user_waits. > > > > But after fsnotify_put_mark_wake() returned, mark->group is still used by > > if (atomic_dec_and_test(&group->user_waits) && group->shutdown) and later. > > > > Is this an issue? > > I don't think this scenario is possible. fsnotify_put_mark_wake() can be > called only for marks attached to objects and these have mark->conn != > NULL and we are sure that fsnotify_destroy_group() will wait for all such > marks to be torn down and freed before dropping last group reference and > freeing the group. > > Honza > -- > Jan Kara > SUSE Labs, CR Ok, thanks for your answer.
Re: [BUG] fs/notify/mark: A potential use after free in fsnotify_put_mark_wake
Hello! On Sun 28-03-21 17:11:43, lyl2...@mail.ustc.edu.cn wrote: > My static analyzer tool reported a use after free in > fsnotify_put_mark_wake > of the file: fs/notify/mark.c. > > In fsnotify_put_mark_wake, it calls fsnotify_put_mark(mark). Inside the > function > fsnotify_put_mark(), if conn is NULL, it will call > fsnotify_final_mark_destroy(mark) > to free mark->group by fsnotify_put_group(group) and return. I also had > inspected > the implementation of fsnotify_put_group() and found that there is no cleanup > operation > about group->user_waits. > > But after fsnotify_put_mark_wake() returned, mark->group is still used by > if (atomic_dec_and_test(&group->user_waits) && group->shutdown) and later. > > Is this an issue? I don't think this scenario is possible. fsnotify_put_mark_wake() can be called only for marks attached to objects and these have mark->conn != NULL and we are sure that fsnotify_destroy_group() will wait for all such marks to be torn down and freed before dropping last group reference and freeing the group. Honza -- Jan Kara SUSE Labs, CR
[BUG] fs/notify/mark: A potential use after free in fsnotify_put_mark_wake
Hi, My static analyzer tool reported a use after free in fsnotify_put_mark_wake of the file: fs/notify/mark.c. In fsnotify_put_mark_wake, it calls fsnotify_put_mark(mark). Inside the function fsnotify_put_mark(), if conn is NULL, it will call fsnotify_final_mark_destroy(mark) to free mark->group by fsnotify_put_group(group) and return. I also had inspected the implementation of fsnotify_put_group() and found that there is no cleanup operation about group->user_waits. But after fsnotify_put_mark_wake() returned, mark->group is still used by if (atomic_dec_and_test(&group->user_waits) && group->shutdown) and later. Is this an issue? Thanks.