Date: Mon, 28 Jan 2019 01:36:56 +0000 (UTC) From: "Pedro F. Giffuni" <pfg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org Subject: svn commit: r343512 - stable/12/sys/fs/ext2fs Message-ID: <201901280136.x0S1aust096023@repo.freebsd.org>
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Author: pfg Date: Mon Jan 28 01:36:55 2019 New Revision: 343512 URL: https://svnweb.freebsd.org/changeset/base/343512 Log: MFC r343459: ext2fs: Add some extra consistency checks for the superblock. Maliciously formed, or badly corrupted, filesystems can cause kernel panics. In general, such acts of foot-shooting can only be accomplished by root, but in a world with VM images that is moving towards automated mounts it is important to have some form of prevention. Reported by: Christopher Krah, Thomas Barabosch, and Jan-Niclas Hilgert of Fraunhofer FKIE. Incidentaly this should also fix a memory corruption issue reported by Dr Silvio Cesare of InfoSect. Huge thanks to all reseachers for making us aware of the issue. admbug: 872, 891 Reviewed by: fsu Obtained from: NetBSD (with minor changes) Modified: stable/12/sys/fs/ext2fs/ext2_vfsops.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/fs/ext2fs/ext2_vfsops.c ============================================================================== --- stable/12/sys/fs/ext2fs/ext2_vfsops.c Mon Jan 28 01:28:17 2019 (r343511) +++ stable/12/sys/fs/ext2fs/ext2_vfsops.c Mon Jan 28 01:36:55 2019 (r343512) @@ -416,7 +416,16 @@ compute_sb_data(struct vnode *devvp, struct ext2fs *es es->e3fs_desc_size); return (EINVAL); } + /* Check for block size = 1K|2K|4K */ + if (es->e2fs_log_bsize > 2) { + printf("ext2fs: bad block size: %d\n", es->e2fs_log_bsize); + return (EINVAL); + } /* Check for group size */ + if (fs->e2fs_bpg == 0) { + printf("ext2fs: zero blocks per group\n"); + return (EINVAL); + } if (fs->e2fs_bpg != fs->e2fs_bsize * 8) { printf("ext2fs: non-standard group size unsupported %d\n", fs->e2fs_bpg); @@ -424,7 +433,21 @@ compute_sb_data(struct vnode *devvp, struct ext2fs *es } fs->e2fs_ipb = fs->e2fs_bsize / EXT2_INODE_SIZE(fs); + if (fs->e2fs_ipg == 0) { + printf("ext2fs: zero inodes per group\n"); + return (EINVAL); + } fs->e2fs_itpg = fs->e2fs_ipg / fs->e2fs_ipb; + /* Check for block consistency */ + if (es->e2fs_first_dblock >= fs->e2fs_bcount) { + printf("ext2fs: invalid first data block\n"); + return (EINVAL); + } + if (fs->e2fs_rbcount > fs->e2fs_bcount || + fs->e2fs_fbcount > fs->e2fs_bcount) { + printf("ext2fs: invalid block count\n"); + return (EINVAL); + } /* s_resuid / s_resgid ? */ fs->e2fs_gcount = howmany(fs->e2fs_bcount - es->e2fs_first_dblock, EXT2_BLOCKS_PER_GROUP(fs));
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