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Message-ID: <CAKFNMok4U8OTVDV0YFDUGotsShSZKST532snzL3fQBVFcUL9TQ@mail.gmail.com>
Date: Sat, 28 Sep 2024 03:18:36 +0900
From: Ryusuke Konishi <konishi.ryusuke@...il.com>
To: Lizhi Xu <lizhi.xu@...driver.com>
Cc: syzbot+8a192e8d090fa9a31135@...kaller.appspotmail.com,
linux-kernel@...r.kernel.org, linux-nilfs@...r.kernel.org,
syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] nilfs2: add ratelimiting to nilfs2 message
On Sat, Sep 28, 2024 at 12:19 AM Lizhi Xu wrote:
>
> Syzbot report a task hung in vcs_open.
> When rec_len too small in nilfs_check_folio, it can result in a huge flood
> of messages being sent to the console. It eventually caused tty to hung when
> retrieving the console_lock().
>
> Reported-by: syzbot+8a192e8d090fa9a31135@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=8a192e8d090fa9a31135
> Signed-off-by: Lizhi Xu <lizhi.xu@...driver.com>
> ---
> fs/nilfs2/dir.c | 24 ++++++++++++++++--------
> 1 file changed, 16 insertions(+), 8 deletions(-)
Thank you for the patch.
I could confirm that the problem is reproducible and that your patch
prevents it, so I will treat this as a nilfs2 side issue.
The patch seems somewhat straightforward, so let me review this a bit
more. I may ask you to make some changes.
Thanks,
Ryusuke Konishi
>
> diff --git a/fs/nilfs2/dir.c b/fs/nilfs2/dir.c
> index fe5b1a30c509..0a89dda75414 100644
> --- a/fs/nilfs2/dir.c
> +++ b/fs/nilfs2/dir.c
> @@ -32,6 +32,7 @@
> #include <linux/pagemap.h>
> #include "nilfs.h"
> #include "page.h"
> +#include <linux/ratelimit.h>
>
> static inline unsigned int nilfs_rec_len_from_disk(__le16 dlen)
> {
> @@ -115,6 +116,7 @@ static bool nilfs_check_folio(struct folio *folio, char *kaddr)
> size_t limit = folio_size(folio);
> struct nilfs_dir_entry *p;
> char *error;
> + static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL * 5, 1);
>
> if (dir->i_size < folio_pos(folio) + limit) {
> limit = dir->i_size - folio_pos(folio);
> @@ -148,9 +150,11 @@ static bool nilfs_check_folio(struct folio *folio, char *kaddr)
> /* Too bad, we had an error */
>
> Ebadsize:
> - nilfs_error(sb,
> - "size of directory #%lu is not a multiple of chunk size",
> - dir->i_ino);
> + if (__ratelimit(&rs)) {
> + nilfs_error(sb,
> + "size of directory #%lu is not a multiple of chunk size",
> + dir->i_ino);
> + }
> goto fail;
> Eshort:
> error = "rec_len is smaller than minimal";
> @@ -167,18 +171,22 @@ static bool nilfs_check_folio(struct folio *folio, char *kaddr)
> Einumber:
> error = "disallowed inode number";
> bad_entry:
> - nilfs_error(sb,
> + if (__ratelimit(&rs)) {
> + nilfs_error(sb,
> "bad entry in directory #%lu: %s - offset=%lu, inode=%lu, rec_len=%zd, name_len=%d",
> dir->i_ino, error, (folio->index << PAGE_SHIFT) + offs,
> (unsigned long)le64_to_cpu(p->inode),
> rec_len, p->name_len);
> + }
> goto fail;
> Eend:
> p = (struct nilfs_dir_entry *)(kaddr + offs);
> - nilfs_error(sb,
> - "entry in directory #%lu spans the page boundary offset=%lu, inode=%lu",
> - dir->i_ino, (folio->index << PAGE_SHIFT) + offs,
> - (unsigned long)le64_to_cpu(p->inode));
> + if (__ratelimit(&rs)) {
> + nilfs_error(sb,
> + "entry in directory #%lu spans the page boundary offset=%lu, inode=%lu",
> + dir->i_ino, (folio->index << PAGE_SHIFT) + offs,
> + (unsigned long)le64_to_cpu(p->inode));
> + }
> fail:
> return false;
> }
> --
> 2.43.0
>
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