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ufs: Rework shortlink handling to avoid subobject overflows
Shortlinks occupy the space of both di_db and di_ib when used. However, everywhere that wants to read or write a shortlink takes a pointer do di_db and promptly runs off the end of it into di_ib. This is fine on most architectures, if a little dodgy. However, on CHERI, the compiler can optionally restrict the bounds on pointers to subobjects to just that subobject, in order to mitigate intra-object buffer overflows, and this is enabled in CheriBSD's pure-capability kernels. Instead, clean this up by inserting a union such that a new di_shortlink can be added with the right size and element type, avoiding the need to cast and allowing the use of the DIP macro to access the field. This also mirrors how the ext2fs code implements extents support, with the exact same structure other than having a uint32_t i_data[] instead of a char di_shortlink[]. Reviewed by: mckusick, jhb Differential Revision: https://reviews.freebsd.org/D33650
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04fd468da0
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@ -525,12 +525,8 @@ dumpino(union dinode *dp, ino_t ino)
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spcl.c_count = 1;
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added = appendextdata(dp);
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writeheader(ino);
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if (sblock->fs_magic == FS_UFS1_MAGIC)
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memmove(buf, (caddr_t)dp->dp1.di_db,
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(u_long)DIP(dp, di_size));
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else
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memmove(buf, (caddr_t)dp->dp2.di_db,
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(u_long)DIP(dp, di_size));
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memmove(buf, DIP(dp, di_shortlink),
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(u_long)DIP(dp, di_size));
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buf[DIP(dp, di_size)] = '\0';
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writerec(buf, 0);
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writeextdata(dp, ino, added);
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@ -136,11 +136,8 @@ printstat(const char *cp, ino_t inum, union dinode *dp)
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if (DIP(dp, di_size) > 0 &&
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DIP(dp, di_size) < sblock.fs_maxsymlinklen &&
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DIP(dp, di_blocks) == 0) {
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if (sblock.fs_magic == FS_UFS1_MAGIC)
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p = (caddr_t)dp->dp1.di_db;
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else
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p = (caddr_t)dp->dp2.di_db;
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printf(" to `%.*s'\n", (int) DIP(dp, di_size), p);
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printf(" to `%.*s'\n", (int) DIP(dp, di_size),
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DIP(dp, di_shortlink));
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} else {
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putchar('\n');
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}
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@ -638,11 +638,8 @@ ufs_open(const char *upath, struct open_file *f)
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bcopy(cp, &namebuf[link_len], len + 1);
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if (link_len < fs->fs_maxsymlinklen) {
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if (fp->f_fs->fs_magic == FS_UFS1_MAGIC)
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cp = (caddr_t)(fp->f_di.di1.di_db);
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else
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cp = (caddr_t)(fp->f_di.di2.di_db);
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bcopy(cp, namebuf, (unsigned) link_len);
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bcopy(DIP(fp, di_shortlink), namebuf,
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(unsigned) link_len);
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} else {
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/*
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* Read file for symbolic link
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@ -342,7 +342,7 @@ ffs_truncate(vp, length, flags, cred)
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if (length != 0)
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panic("ffs_truncate: partial truncate of symlink");
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#endif
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bzero(SHORTLINK(ip), (u_int)ip->i_size);
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bzero(DIP(ip, i_shortlink), (u_int)ip->i_size);
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ip->i_size = 0;
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DIP_SET(ip, i_size, 0);
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UFS_INODE_SET_FLAG(ip, IN_SIZEMOD | IN_CHANGE | IN_UPDATE);
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@ -145,8 +145,16 @@ struct ufs2_dinode {
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u_int32_t di_flags; /* 88: Status flags (chflags). */
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u_int32_t di_extsize; /* 92: External attributes size. */
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ufs2_daddr_t di_extb[UFS_NXADDR];/* 96: External attributes block. */
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ufs2_daddr_t di_db[UFS_NDADDR]; /* 112: Direct disk blocks. */
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ufs2_daddr_t di_ib[UFS_NIADDR]; /* 208: Indirect disk blocks. */
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union {
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struct {
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ufs2_daddr_t di_db /* 112: Direct disk blocks. */
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[UFS_NDADDR];
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ufs2_daddr_t di_ib /* 208: Indirect disk blocks. */
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[UFS_NIADDR];
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};
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char di_shortlink /* 112: Embedded symbolic link. */
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[(UFS_NDADDR + UFS_NIADDR) * sizeof(ufs2_daddr_t)];
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};
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u_int64_t di_modrev; /* 232: i_modrev for NFSv4 */
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uint32_t di_freelink; /* 240: SUJ: Next unlinked inode. */
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uint32_t di_ckhash; /* 244: if CK_INODE, its check-hash */
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@ -179,8 +187,16 @@ struct ufs1_dinode {
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int32_t di_mtimensec; /* 28: Last modified time. */
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int32_t di_ctime; /* 32: Last inode change time. */
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int32_t di_ctimensec; /* 36: Last inode change time. */
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ufs1_daddr_t di_db[UFS_NDADDR]; /* 40: Direct disk blocks. */
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ufs1_daddr_t di_ib[UFS_NIADDR]; /* 88: Indirect disk blocks. */
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union {
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struct {
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ufs1_daddr_t di_db /* 40: Direct disk blocks. */
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[UFS_NDADDR];
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ufs1_daddr_t di_ib /* 88: Indirect disk blocks. */
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[UFS_NIADDR];
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};
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char di_shortlink /* 40: Embedded symbolic link. */
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[(UFS_NDADDR + UFS_NIADDR) * sizeof(ufs1_daddr_t)];
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};
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u_int32_t di_flags; /* 100: Status flags (chflags). */
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u_int32_t di_blocks; /* 104: Blocks actually held. */
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u_int32_t di_gen; /* 108: Generation number. */
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@ -246,8 +246,6 @@ I_IS_UFS2(const struct inode *ip)
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(ip)->i_din2->d##field = (val); \
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} while (0)
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#define SHORTLINK(ip) (I_IS_UFS1(ip) ? \
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(caddr_t)(ip)->i_din1->di_db : (caddr_t)(ip)->i_din2->di_db)
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#define IS_SNAPSHOT(ip) ((ip)->i_flags & SF_SNAPSHOT)
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/*
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@ -2311,7 +2311,7 @@ ufs_symlink(ap)
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len = strlen(ap->a_target);
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if (len < VFSTOUFS(vp->v_mount)->um_maxsymlinklen) {
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ip = VTOI(vp);
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bcopy(ap->a_target, SHORTLINK(ip), len);
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bcopy(ap->a_target, DIP(ip, i_shortlink), len);
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ip->i_size = len;
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DIP_SET(ip, i_size, len);
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UFS_INODE_SET_FLAG(ip, IN_SIZEMOD | IN_CHANGE | IN_UPDATE);
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@ -2481,7 +2481,7 @@ ufs_readlink(ap)
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isize = ip->i_size;
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if (isize < VFSTOUFS(vp->v_mount)->um_maxsymlinklen)
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return (uiomove(SHORTLINK(ip), isize, ap->a_uio));
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return (uiomove(DIP(ip, i_shortlink), isize, ap->a_uio));
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return (VOP_READ(vp, ap->a_uio, 0, ap->a_cred));
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}
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@ -99,8 +99,8 @@ prtblknos(fs, dp)
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if (size < fs->fs_maxsymlinklen) {
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printf("symbolic link referencing %s\n",
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(fs->fs_magic == FS_UFS1_MAGIC) ?
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(char *)dp->dp1.di_db :
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(char *)dp->dp2.di_db);
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dp->dp1.di_shortlink :
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dp->dp2.di_shortlink);
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return;
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}
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printf("symbolic link\n");
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@ -704,7 +704,7 @@ ffs_build_dinode1(struct ufs1_dinode *dinp, dirbuf_t *dbufp, fsnode *cur,
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} else if (S_ISLNK(cur->type)) { /* symlink */
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slen = strlen(cur->symlink);
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if (slen < UFS1_MAXSYMLINKLEN) { /* short link */
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memcpy(dinp->di_db, cur->symlink, slen);
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memcpy(dinp->di_shortlink, cur->symlink, slen);
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} else
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membuf = cur->symlink;
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dinp->di_size = slen;
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@ -763,7 +763,7 @@ ffs_build_dinode2(struct ufs2_dinode *dinp, dirbuf_t *dbufp, fsnode *cur,
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} else if (S_ISLNK(cur->type)) { /* symlink */
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slen = strlen(cur->symlink);
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if (slen < UFS2_MAXSYMLINKLEN) { /* short link */
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memcpy(dinp->di_db, cur->symlink, slen);
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memcpy(dinp->di_shortlink, cur->symlink, slen);
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} else
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membuf = cur->symlink;
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dinp->di_size = slen;
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@ -68,7 +68,7 @@ struct inode {
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#define i_ffs1_mtimensec i_din.ffs1_din.di_mtimensec
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#define i_ffs1_nlink i_din.ffs1_din.di_nlink
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#define i_ffs1_rdev i_din.ffs1_din.di_rdev
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#define i_ffs1_shortlink i_din.ffs1_din.db
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#define i_ffs1_shortlink i_din.ffs1_din.di_shortlink
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#define i_ffs1_size i_din.ffs1_din.di_size
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#define i_ffs1_uid i_din.ffs1_din.di_uid
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@ -89,7 +89,7 @@ struct inode {
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#define i_ffs2_mtimensec i_din.ffs2_din.di_mtimensec
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#define i_ffs2_nlink i_din.ffs2_din.di_nlink
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#define i_ffs2_rdev i_din.ffs2_din.di_rdev
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#define i_ffs2_shortlink i_din.ffs2_din.db
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#define i_ffs2_shortlink i_din.ffs2_din.di_shortlink
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#define i_ffs2_size i_din.ffs2_din.di_size
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#define i_ffs2_uid i_din.ffs2_din.di_uid
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