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Sun, 18 Jan 2026 11:05:25 -0800 (PST) From: Jiasheng Jiang To: markus.elfring@web.de Cc: jiashengjiangcool@gmail.com, jlbec@evilplan.org, joseph.qi@linux.alibaba.com, linux-kernel@vger.kernel.org, mark@fasheh.com, ocfs2-devel@lists.linux.dev, stable@vger.kernel.org Subject: [PATCH v2] ocfs2: fix NULL pointer dereference in ocfs2_get_refcount_rec Date: Sun, 18 Jan 2026 19:05:23 +0000 Message-Id: <20260118190523.42581-1-jiashengjiangcool@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" In ocfs2_get_refcount_rec(), the 'rec' pointer is initialized to NULL. If the extent list is empty (el->l_next_free_rec =3D=3D 0), the loop skips assignment, leaving 'rec' as NULL and 'found' as 0. Currently, the code skips the 'if (found)' block but proceeds directly to dereference 'rec' at line 767 (le64_to_cpu(rec->e_blkno)), causing a NULL pointer dereference panic. This patch adds an 'else' branch to the 'if (found)' check. If no valid record is found, it reports a filesystem error and exits, preventing the invalid memory access. Fixes: e73a819db9c2 ("ocfs2: Add support for incrementing refcount in the t= ree.") Signed-off-by: Jiasheng Jiang --- Changelog: v1 -> v2: 1. Add a Fixes tag. --- fs/ocfs2/refcounttree.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/ocfs2/refcounttree.c b/fs/ocfs2/refcounttree.c index c92e0ea85bca..464bdd6e0a8e 100644 --- a/fs/ocfs2/refcounttree.c +++ b/fs/ocfs2/refcounttree.c @@ -1122,6 +1122,11 @@ static int ocfs2_get_refcount_rec(struct ocfs2_cachi= ng_info *ci, =20 if (cpos_end < low_cpos + len) len =3D cpos_end - low_cpos; + } else { + ret =3D ocfs2_error(sb, "Refcount tree %llu has no extent record coverin= g cpos %u\n", + (unsigned long long)ocfs2_metadata_cache_owner(ci), + low_cpos); + goto out; } =20 ret =3D ocfs2_read_refcount_block(ci, le64_to_cpu(rec->e_blkno), --=20 2.25.1