If the directory is corrupted and the number of nlinks is less than 2 (valid nlinks have at least 2), then when the directory is deleted, the minix_rmdir will try to reduce the nlinks(unsigned int) to a negative value.
Make nlinks validity check for directory.
Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Andrey Kriulin kitotavrik.media@gmail.com Signed-off-by: Andrey Kriulin kitotavrik.s@gmail.com --- v2: Move nlinks validaty check to V[12]_minix_iget() per Jan Kara jack@suse.cz request. Change return error code to EUCLEAN. Don't block directory in r/o mode per Al Viro viro@zeniv.linux.org.uk request.
fs/minix/inode.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/fs/minix/inode.c b/fs/minix/inode.c index f007e389d5d2..d815397b8b0d 100644 --- a/fs/minix/inode.c +++ b/fs/minix/inode.c @@ -517,6 +517,14 @@ static struct inode *V1_minix_iget(struct inode *inode) iget_failed(inode); return ERR_PTR(-ESTALE); } + if (S_ISDIR(raw_inode->i_mode) && raw_inode->i_nlinks < 2) { + printk("MINIX-fs: inode directory with corrupted number of links"); + if (!sb_rdonly(inode->i_sb)) { + brelse(bh); + iget_failed(inode); + return ERR_PTR(-EUCLEAN); + } + } inode->i_mode = raw_inode->i_mode; i_uid_write(inode, raw_inode->i_uid); i_gid_write(inode, raw_inode->i_gid); @@ -555,6 +563,14 @@ static struct inode *V2_minix_iget(struct inode *inode) iget_failed(inode); return ERR_PTR(-ESTALE); } + if (S_ISDIR(raw_inode->i_mode) && raw_inode->i_nlinks < 2) { + printk("MINIX-fs: inode directory with corrupted number of links"); + if (!sb_rdonly(inode->i_sb)) { + brelse(bh); + iget_failed(inode); + return ERR_PTR(-EUCLEAN); + } + } inode->i_mode = raw_inode->i_mode; i_uid_write(inode, raw_inode->i_uid); i_gid_write(inode, raw_inode->i_gid);