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Mon, 30 Jun 2025 01:35:53 -0700 (PDT) Received: from manjaro.domain.name ([2401:4900:1c31:3031:bed6:689:68b3:ea6e]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-74af57ebcb5sm8320722b3a.151.2025.06.30.01.35.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Jun 2025 01:35:53 -0700 (PDT) From: Pranav Tyagi To: ocfs2-devel@oss.oracle.com, linux-kernel@vger.kernel.org Cc: mark@fasheh.com, jlbec@evilplan.org, joseph.qi@linux.alibaba.com, pvmohammedanees2003@gmail.com, akpm@linux-foundation.org, gregkh@linuxfoundation.org, sashal@kernel.org, skhan@linuxfoundation.org, stable@vger.kernel.org, linux-kernel-mentees@lists.linux.dev, syzbot+e0055ea09f1f5e6fabdd@syzkaller.appspotmail.com, Junxiao Bi , Changwei Ge , Gang He , Jun Piao , Pranav Tyagi Subject: [PATCH 5.15.y] ocfs2: fix deadlock in ocfs2_get_system_file_inode Date: Mon, 30 Jun 2025 14:05:42 +0530 Message-ID: <20250630083542.10121-1-pranav.tyagi03@gmail.com> X-Mailer: git-send-email 2.49.0 Precedence: bulk X-Mailing-List: linux-kernel-mentees@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Mohammed Anees [ Upstream commit 7bf1823e010e8db2fb649c790bd1b449a75f52d8 ] syzbot has found a possible deadlock in ocfs2_get_system_file_inode [1]. The scenario is depicted here, CPU0 CPU1 lock(&ocfs2_file_ip_alloc_sem_key); lock(&osb->system_file_mutex); lock(&ocfs2_file_ip_alloc_sem_key); lock(&osb->system_file_mutex); The function calls which could lead to this are: CPU0 ocfs2_mknod - lock(&ocfs2_file_ip_alloc_sem_key); . . . ocfs2_get_system_file_inode - lock(&osb->system_file_mutex); CPU1 - ocfs2_fill_super - lock(&osb->system_file_mutex); . . . ocfs2_read_virt_blocks - lock(&ocfs2_file_ip_alloc_sem_key); This issue can be resolved by making the down_read -> down_read_try in the ocfs2_read_virt_blocks. [1] https://syzkaller.appspot.com/bug?extid=e0055ea09f1f5e6fabdd [ Backport to 5.15: context cleanly applied with no semantic changes. Build-tested. ] Link: https://lkml.kernel.org/r/20240924093257.7181-1-pvmohammedanees2003@gmail.com Signed-off-by: Mohammed Anees Reviewed-by: Joseph Qi Reported-by: Closes: https://syzkaller.appspot.com/bug?extid=e0055ea09f1f5e6fabdd Tested-by: syzbot+e0055ea09f1f5e6fabdd@syzkaller.appspotmail.com Cc: Mark Fasheh Cc: Joel Becker Cc: Junxiao Bi Cc: Changwei Ge Cc: Gang He Cc: Jun Piao Cc: Signed-off-by: Andrew Morton Signed-off-by: Pranav Tyagi --- fs/ocfs2/extent_map.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c index 70a768b623cf..f7672472fa82 100644 --- a/fs/ocfs2/extent_map.c +++ b/fs/ocfs2/extent_map.c @@ -973,7 +973,13 @@ int ocfs2_read_virt_blocks(struct inode *inode, u64 v_block, int nr, } while (done < nr) { - down_read(&OCFS2_I(inode)->ip_alloc_sem); + if (!down_read_trylock(&OCFS2_I(inode)->ip_alloc_sem)) { + rc = -EAGAIN; + mlog(ML_ERROR, + "Inode #%llu ip_alloc_sem is temporarily unavailable\n", + (unsigned long long)OCFS2_I(inode)->ip_blkno); + break; + } rc = ocfs2_extent_map_get_blocks(inode, v_block + done, &p_block, &p_count, NULL); up_read(&OCFS2_I(inode)->ip_alloc_sem); -- 2.49.0