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[34.83.123.78]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-cc72aefc0a6sm1360139a12.28.2026.09.19.15.25.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 15:25:58 -0700 (PDT) From: Hui Peng To: brauner@kernel.org, jack@suse.cz, kees@kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] ufs: fix cylinder structures slab-OOB write, div-by-zero, and error cleanup Date: Sat, 19 Sep 2026 22:25:57 +0000 Message-ID: <20260919222558.3792924-1-benquike@gmail.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Fix three superblock validation bugs in fs/ufs/super.c: 1. In ufs_read_cylinder_structures(), allocate u_space according to the actual cylinder group summary size and bounds-check s_ncg and s_cssize to prevent a 1024..4096-byte memcpy into a kmalloc-16 buffer. 2. In ufs_fill_super(), validate uspi->s_inopf, uspi->s_ipg, and uspi->s_fpg against zero to prevent hardware divide-by-zero (#DE) traps. 3. On the ufs_fill_super() failure path after d_make_root(), clear or avoid leaving sb->s_root populated when sbi is freed so ufs_put_super() does not dereference NULL sb->s_fs_info. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Assisted-by: LLM Signed-off-by: Hui Peng --- diff --git a/fs/ufs/super.c b/fs/ufs/super.c index 3569ac92b065..7d2eb3cbdcf0 100644 --- a/fs/ufs/super.c +++ b/fs/ufs/super.c @@ -455,7 +455,7 @@ static int ufs_read_cylinder_structures(struct super_block *sb) { struct ufs_sb_info *sbi = UFS_SB(sb); struct ufs_sb_private_info *uspi = sbi->s_uspi; - unsigned char * base, * space; + unsigned char *base = NULL, *space; unsigned size, blks, i; UFSD("ENTER\n"); @@ -465,17 +465,21 @@ static int ufs_read_cylinder_structures(struct super_block *sb) * on the device. */ size = uspi->s_cssize; + if (!size || size < (size_t)uspi->s_ncg * sizeof(struct ufs_csum)) + goto failed; blks = (size + uspi->s_fsize - 1) >> uspi->s_fshift; base = space = kmalloc(size, GFP_NOFS); if (!base) goto failed; sbi->s_csp = (struct ufs_csum *)space; for (i = 0; i < blks; i++) { + size_t copy_len = min_t(size_t, size - (space - base), + uspi->s_fsize); struct buffer_head *bh = sb_bread(sb, uspi->s_csaddr + i); if (!bh) goto failed; - memcpy(space, bh->b_data, uspi->s_fsize); - space += uspi->s_fsize; + memcpy(space, bh->b_data, copy_len); + space += copy_len; brelse (bh); } @@ -595,15 +599,19 @@ static void ufs_put_super_internal(struct super_block *sb) size = uspi->s_cssize; blks = (size + uspi->s_fsize - 1) >> uspi->s_fshift; base = space = (char*) sbi->s_csp; - for (i = 0; i < blks; i++, space += uspi->s_fsize) { + for (i = 0; i < blks; i++) { + size_t copy_len = min_t(size_t, size - (space - base), + uspi->s_fsize); struct buffer_head *bh = sb_bread(sb, uspi->s_csaddr + i); if (unlikely(!bh)) { // better than an oops... ufs_panic(sb, __func__, "can't write part of cylinder group summary"); + space += copy_len; continue; } - memcpy(bh->b_data, space, uspi->s_fsize); + memcpy(bh->b_data, space, copy_len); + space += copy_len; mark_buffer_dirty(bh); brelse(bh); } @@ -1179,6 +1187,11 @@ static int ufs_fill_super(struct super_block *sb, struct fs_context *fc) uspi->s_nspfshift = uspi->s_fshift - UFS_SECTOR_BITS; uspi->s_nspb = uspi->s_nspf << uspi->s_fpbshift; uspi->s_inopf = uspi->s_inopb >> uspi->s_fpbshift; + if (!uspi->s_inopf || !uspi->s_ipg) { + ufs_error(sb, __func__, "invalid fs_inopb (%u) or fs_ipg (%u)\n", + uspi->s_inopb, uspi->s_ipg); + goto failed; + } uspi->s_bpf = uspi->s_fsize << 3; uspi->s_bpfshift = uspi->s_fshift + 3; uspi->s_bpfmask = uspi->s_bpf - 1; @@ -1211,18 +1224,23 @@ static int ufs_fill_super(struct super_block *sb, struct fs_context *fc) inode = ufs_iget(sb, UFS_ROOTINO); if (IS_ERR(inode)) { ret = PTR_ERR(inode); - goto failed; + goto failed_put_cyl; } sb->s_root = d_make_root(inode); if (!sb->s_root) { ret = -ENOMEM; - goto failed; + goto failed_put_cyl; } UFSD("EXIT\n"); return 0; +failed_put_cyl: + if (!sb_rdonly(sb)) + ufs_put_super_internal(sb); failed: + dput(sb->s_root); + sb->s_root = NULL; if (ubh) ubh_brelse_uspi (uspi); kfree (uspi);