ovl: avoid possible inode number collisions with xino=on (dfe51d47) · Commits · 戴 / test

fs/overlayfs/inode.c

+29 −10

Original line number	Diff line number	Diff line
		@@ -79,6 +79,7 @@ static int ovl_map_dev_ino(struct dentry dentry, struct kstat stat, int fsid)
		{
		bool samefs = ovl_same_fs(dentry->d_sb);
		unsigned int xinobits = ovl_xino_bits(dentry->d_sb);
		unsigned int xinoshift = 64 - xinobits;

		if (samefs) {
		/*
		@@ -89,20 +90,20 @@ static int ovl_map_dev_ino(struct dentry dentry, struct kstat stat, int fsid)
		stat->dev = dentry->d_sb->s_dev;
		return 0;
		} else if (xinobits) {
		unsigned int shift = 64 - xinobits;
		/*
		* All inode numbers of underlying fs should not be using the
		* high xinobits, so we use high xinobits to partition the
		* overlay st_ino address space. The high bits holds the fsid
		* (upper fsid is 0). This way overlay inode numbers are unique
		* and all inodes use overlay st_dev. Inode numbers are also
		* persistent for a given layer configuration.
		* (upper fsid is 0). The lowest xinobit is reserved for mapping
		* the non-peresistent inode numbers range in case of overflow.
		* This way all overlay inode numbers are unique and use the
		* overlay st_dev.
		*/
		if (stat->ino >> shift) {
		if (unlikely(stat->ino >> xinoshift)) {
		pr_warn_ratelimited("inode number too big (%pd2, ino=%llu, xinobits=%d)\n",
		dentry, stat->ino, xinobits);
		} else {
		stat->ino \|= ((u64)fsid) << shift;
		stat->ino \|= ((u64)fsid) << (xinoshift + 1);
		stat->dev = dentry->d_sb->s_dev;
		return 0;
		}
		@@ -573,6 +574,7 @@ static void ovl_next_ino(struct inode *inode)
		static void ovl_map_ino(struct inode *inode, unsigned long ino, int fsid)
		{
		int xinobits = ovl_xino_bits(inode->i_sb);
		unsigned int xinoshift = 64 - xinobits;

		/*
		* When d_ino is consistent with st_ino (samefs or i_ino has enough
		@@ -582,11 +584,28 @@ static void ovl_map_ino(struct inode *inode, unsigned long ino, int fsid)
		* with d_ino also causes nfsd readdirplus to fail.
		*/
		inode->i_ino = ino;
		if (ovl_same_dev(inode->i_sb)) {
		if (xinobits && fsid && !(ino >> (64 - xinobits)))
		inode->i_ino \|= (unsigned long)fsid << (64 - xinobits);
		} else if (S_ISDIR(inode->i_mode)) {
		if (ovl_same_fs(inode->i_sb)) {
		return;
		} else if (xinobits && likely(!(ino >> xinoshift))) {
		inode->i_ino \|= (unsigned long)fsid << (xinoshift + 1);
		return;
		}

		/*
		* For directory inodes on non-samefs with xino disabled or xino
		* overflow, we allocate a non-persistent inode number, to be used for
		* resolving st_ino collisions in ovl_map_dev_ino().
		*
		* To avoid ino collision with legitimate xino values from upper
		* layer (fsid 0), use the lowest xinobit to map the non
		* persistent inode numbers to the unified st_ino address space.
		*/
		if (S_ISDIR(inode->i_mode)) {
		ovl_next_ino(inode);
		if (xinobits) {
		inode->i_ino &= ~0UL >> xinobits;
		inode->i_ino \|= 1UL << xinoshift;
		}
		}
		}

fs/overlayfs/readdir.c

+8 −2

Original line number	Diff line number	Diff line
		@@ -440,13 +440,19 @@ static struct ovl_dir_cache ovl_cache_get(struct dentry dentry)
		static u64 ovl_remap_lower_ino(u64 ino, int xinobits, int fsid,
		const char *name, int namelen)
		{
		if (ino >> (64 - xinobits)) {
		unsigned int xinoshift = 64 - xinobits;

		if (unlikely(ino >> xinoshift)) {
		pr_warn_ratelimited("d_ino too big (%.*s, ino=%llu, xinobits=%d)\n",
		namelen, name, ino, xinobits);
		return ino;
		}

		return ino \| ((u64)fsid) << (64 - xinobits);
		/*
		* The lowest xinobit is reserved for mapping the non-peresistent inode
		* numbers range, but this range is only exposed via st_ino, not here.
		*/
		return ino \| ((u64)fsid) << (xinoshift + 1);
		}

		/*

fs/overlayfs/super.c

+8 −5

Original line number	Diff line number	Diff line
		@@ -1483,7 +1483,8 @@ static int ovl_get_layers(struct super_block sb, struct ovl_fs ofs,
		* free high bits in underlying fs to hold the unique fsid.
		* If overlayfs does encounter underlying inodes using the high xino
		* bits reserved for fsid, it emits a warning and uses the original
		* inode number.
		* inode number or a non persistent inode number allocated from a
		* dedicated range.
		*/
		if (ofs->numfs - !ofs->upper_mnt == 1) {
		if (ofs->config.xino == OVL_XINO_ON)
		@@ -1494,11 +1495,13 @@ static int ovl_get_layers(struct super_block sb, struct ovl_fs ofs,
		} else if (ofs->config.xino == OVL_XINO_ON && ofs->xino_mode < 0) {
		/*
		* This is a roundup of number of bits needed for encoding
		* fsid, where fsid 0 is reserved for upper fs even with
		* lower only overlay.
		* fsid, where fsid 0 is reserved for upper fs (even with
		* lower only overlay) +1 extra bit is reserved for the non
		* persistent inode number range that is used for resolving
		* xino lower bits overflow.
		*/
		BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 31);
		ofs->xino_mode = ilog2(ofs->numfs - 1) + 1;
		BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 30);
		ofs->xino_mode = ilog2(ofs->numfs - 1) + 2;
		}

		if (ofs->xino_mode > 0) {

Admin message