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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> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII 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