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([2401:4900:88f7:9fa5:7c44:c012:b691:46c1]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-237d83efa44sm112033045ad.77.2025.06.24.10.10.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Jun 2025 10:10:46 -0700 (PDT) From: Abinash Singh X-Google-Original-From: Abinash Singh To: linux-f2fs-devel@lists.sourceforge.net Cc: abinashlalotra@gmail.com, abinashsinghlalotra@gmail.com, chao@kernel.org, jaegeuk@kernel.org, linux-kernel@vger.kernel.org, syzbot+b8c1d60e95df65e827d4@syzkaller.appspotmail.com Subject: [PATCH v3] f2fs: fix KMSAN uninit-value in extent_info usage Date: Tue, 24 Jun 2025 22:39:48 +0530 Message-ID: <20250624170948.59013-1-abinashsinghlalotra@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <1669c05c-7468-4347-a924-cfc4145c8c75@kernel.org> References: <1669c05c-7468-4347-a924-cfc4145c8c75@kernel.org> 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" KMSAN reported a use of uninitialized value in `__is_extent_mergeable()` and `__is_back_mergeable()` via the read extent tree path. The root cause is that `get_read_extent_info()` only initializes three fields (`fofs`, `blk`, `len`) of `struct extent_info`, leaving the remaining fields uninitialized. This leads to undefined behavior when those fields are accessed later, especially during=20 extent merging. Fix it by zero-initializing the `extent_info` struct before population. Reported-by: syzbot+b8c1d60e95df65e827d4@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3Db8c1d60e95df65e827d4 Fixes: a28ef1f5aebe ("f2fs: maintain extent cache in separated file") Signed-off-by: Abinash Singh Reviewed-by: Chao Yu --- v3 : Added Fixes and Closes tags --- fs/f2fs/extent_cache.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c index cfe925a3d555..4ce19a310f38 100644 --- a/fs/f2fs/extent_cache.c +++ b/fs/f2fs/extent_cache.c @@ -414,7 +414,7 @@ void f2fs_init_read_extent_tree(struct inode *inode, st= ruct folio *ifolio) struct f2fs_extent *i_ext =3D &F2FS_INODE(&ifolio->page)->i_ext; struct extent_tree *et; struct extent_node *en; - struct extent_info ei; + struct extent_info ei =3D {0}; =20 if (!__may_extent_tree(inode, EX_READ)) { /* drop largest read extent */ --=20 2.43.0