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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id 00721157ae682-86c10c9461esm43081537b3.7.2026.09.03.08.15.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Sep 2026 08:15:27 -0700 (PDT) Date: Thu, 3 Sep 2026 08:15:14 -0700 (PDT) From: Hugh Dickins To: Jan Kara cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, ocfs2-devel@lists.linux.dev, Joseph Qi , Hugh Dickins , Baolin Wang , Farhad Alemi Subject: Re: [PATCH v2 2/2] shmem: Refuse to enable tmpfs format for another filesystem In-Reply-To: <20260903090508.1360863-4-jack@suse.cz> Message-ID: <3b119174-7b10-6eb6-7aff-462949fcb49a@google.com> References: <20260903090053.13120-1-jack@suse.cz> <20260903090508.1360863-4-jack@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 9291720006 X-Stat-Signature: z3pa5e9wfjj9apc9tm9zez8jawzbofq3 X-HE-Tag: 1788448529-341280 X-HE-Meta: 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 jrNIy3ar XGUoweJv5E+I2NhsHmPea/ThsqD5QGtqSwR0ID+usRmtsRthyRwIAItzNpQ94gqb5JZGISlGTZXLjPP4xFj60KtNQ3DD5PzSJqel64aONjzqYd0cAunB3ZPXh4nxtYsIvOxbbaQQ3S2XNfrI2Nb4LkBG0nv11CX45TGWPHr4LKIXwHPBtftLuqwj4jVfn5LnHs8FbOW1Sd8OmXHol/yiezVtVNHuGXmuOLPHXj+jH80cZmcEaFcOPs0vUXMxwp7OxpybDgVpCl4C6lpIoj0rFu1ox+2Qdn8qt+WJbA9YdO4bwQHhyWkO7uDp98ZGmJZN5pVpYM5H97johTwcfhXwiikO4SmNbo66XTYmFCE6spAqd5C93/ryXjvrL3CaZCGLLDaFY Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 3 Sep 2026, Jan Kara wrote: > It is possible to issue Q_QUOTAON quotactl(2) e.g. for ext4 filesystem > requesting to enable quota using tmpfs quota format. With suitable > passed arguments this can actually succeed in enabling tmpfs quota > format on top of ext4 filesystem which leads to crashes later in > dquot_acquire(). As tmpfs quota format is intended for tmpfs > filesystems only, verify we are indeed enabling quotas there. > > Reported-by: Farhad Alemi > Signed-off-by: Jan Kara Acked-by: Hugh Dickins Thanks: yes, please do route it through your tree. > --- > mm/shmem_quota.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/mm/shmem_quota.c b/mm/shmem_quota.c > index d0b92d6da50f..a3fa4bd93e75 100644 > --- a/mm/shmem_quota.c > +++ b/mm/shmem_quota.c > @@ -30,6 +30,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -54,6 +55,10 @@ struct quota_id { > > static int shmem_check_quota_file(struct super_block *sb, int type) > { > + /* Verify enabling happens on tmpfs superblock */ > + if (sb->s_magic != TMPFS_MAGIC) > + return 0; > + > /* There is no real quota file, nothing to do */ > return 1; > } > -- > 2.51.0