From da27e0a0e5f655f0d58d4e153c3182bb2b290f64 Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Tue, 11 Aug 2020 18:35:24 -0700 Subject: [PATCH] fs/minix: check return value of sb_getblk() Patch series "fs/minix: fix syzbot bugs and set s_maxbytes". This series fixes all syzbot bugs in the minix filesystem: KASAN: null-ptr-deref Write in get_block KASAN: use-after-free Write in get_block KASAN: use-after-free Read in get_block WARNING in inc_nlink KMSAN: uninit-value in get_block WARNING in drop_nlink It also fixes the minix filesystem to set s_maxbytes correctly, so that userspace sees the correct behavior when exceeding the max file size. This patch (of 6): sb_getblk() can fail, so check its return value. This fixes a NULL pointer dereference. Originally from Qiujun Huang. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot+4a88b2b9dc280f47baf4@syzkaller.appspotmail.com Signed-off-by: Eric Biggers Signed-off-by: Andrew Morton Cc: Qiujun Huang Cc: Alexander Viro Cc: Link: http://lkml.kernel.org/r/20200628060846.682158-1-ebiggers@kernel.org Link: http://lkml.kernel.org/r/20200628060846.682158-2-ebiggers@kernel.org Signed-off-by: Linus Torvalds --- fs/minix/itree_common.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/fs/minix/itree_common.c b/fs/minix/itree_common.c index 043c3fdbc8e7..446148792f41 100644 --- a/fs/minix/itree_common.c +++ b/fs/minix/itree_common.c @@ -75,6 +75,7 @@ static int alloc_branch(struct inode *inode, int n = 0; int i; int parent = minix_new_block(inode); + int err = -ENOSPC; branch[0].key = cpu_to_block(parent); if (parent) for (n = 1; n < num; n++) { @@ -85,6 +86,11 @@ static int alloc_branch(struct inode *inode, break; branch[n].key = cpu_to_block(nr); bh = sb_getblk(inode->i_sb, parent); + if (!bh) { + minix_free_block(inode, nr); + err = -ENOMEM; + break; + } lock_buffer(bh); memset(bh->b_data, 0, bh->b_size); branch[n].bh = bh; @@ -103,7 +109,7 @@ static int alloc_branch(struct inode *inode, bforget(branch[i].bh); for (i = 0; i < n; i++) minix_free_block(inode, block_to_cpu(branch[i].key)); - return -ENOSPC; + return err; } static inline int splice_branch(struct inode *inode,