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Thu, 3 Sep 2026 09:05:15 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 5TGBIEs4mWrETAAAD6G6ig (envelope-from ); Thu, 03 Sep 2026 09:05:15 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id E4D5DA13B8; Thu, 03 Sep 2026 11:05:14 +0200 (CEST) From: Jan Kara To: Cc: , ocfs2-devel@lists.linux.dev, Joseph Qi , Hugh Dickins , Baolin Wang , Farhad Alemi , Jan Kara Subject: [PATCH v2 2/2] shmem: Refuse to enable tmpfs format for another filesystem Date: Thu, 3 Sep 2026 11:05:05 +0200 Message-ID: <20260903090508.1360863-4-jack@suse.cz> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260903090053.13120-1-jack@suse.cz> References: <20260903090053.13120-1-jack@suse.cz> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1198; i=jack@suse.cz; h=from:subject; bh=yq74qpUyYYBh+XhkRlhY9CvlmFz4Sh7DR+W9lw8EnSI=; 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MIME_TRACE(0.00)[0:+]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_THREE(0.00)[3]; RCPT_COUNT_SEVEN(0.00)[8]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; TO_DN_SOME(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,suse.cz:email,suse.cz:mid,berkeley.edu:email] 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 --- 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