From 01c5015da5b824cebb722d32f8804fc328ba613f Mon Sep 17 00:00:00 2001 From: Sriram Rajagopalan Date: Thu, 17 Oct 2019 16:59:27 +0800 Subject: [PATCH] Android Security Bulletin - November 2019-11 - Kernel components ext4 filesystem - CVE-2019-11833 [1/1] PD#OTT-6798 Problem: ext4: zero out the unused memory region in the extent tree block Solution: This commit zeroes out the unused memory region in the buffer_head corresponding to the extent metablock after writing the extent header and the corresponding extent node entries. This is done to prevent random uninitialized data from getting into the filesystem when the extent block is synced. This fixes CVE-2019-11833. Verify: Raven Change-Id: I5c6aae01432f5517b539312507e59e8dfb9c25eb Signed-off-by: Sriram Rajagopalan Signed-off-by: Theodore Ts'o Cc: stable@kernel.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Hanjie Lin --- fs/ext4/extents.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 106a5bb3ae68..b2ba9955fa11 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -1047,6 +1047,7 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode, __le32 border; ext4_fsblk_t *ablocks = NULL; /* array of allocated blocks */ int err = 0; + size_t ext_size = 0; /* make decision: where to split? */ /* FIXME: now decision is simplest: at current extent */ @@ -1138,6 +1139,10 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode, le16_add_cpu(&neh->eh_entries, m); } + /* zero out unused area in the extent block */ + ext_size = sizeof(struct ext4_extent_header) + + sizeof(struct ext4_extent) * le16_to_cpu(neh->eh_entries); + memset(bh->b_data + ext_size, 0, inode->i_sb->s_blocksize - ext_size); ext4_extent_block_csum_set(inode, neh); set_buffer_uptodate(bh); unlock_buffer(bh); @@ -1217,6 +1222,11 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode, sizeof(struct ext4_extent_idx) * m); le16_add_cpu(&neh->eh_entries, m); } + /* zero out unused area in the extent block */ + ext_size = sizeof(struct ext4_extent_header) + + (sizeof(struct ext4_extent) * le16_to_cpu(neh->eh_entries)); + memset(bh->b_data + ext_size, 0, + inode->i_sb->s_blocksize - ext_size); ext4_extent_block_csum_set(inode, neh); set_buffer_uptodate(bh); unlock_buffer(bh); @@ -1282,6 +1292,7 @@ static int ext4_ext_grow_indepth(handle_t *handle, struct inode *inode, ext4_fsblk_t newblock, goal = 0; struct ext4_super_block *es = EXT4_SB(inode->i_sb)->s_es; int err = 0; + size_t ext_size = 0; /* Try to prepend new index to old one */ if (ext_depth(inode)) @@ -1307,9 +1318,11 @@ static int ext4_ext_grow_indepth(handle_t *handle, struct inode *inode, goto out; } + ext_size = sizeof(EXT4_I(inode)->i_data); /* move top-level index/leaf into new block */ - memmove(bh->b_data, EXT4_I(inode)->i_data, - sizeof(EXT4_I(inode)->i_data)); + memmove(bh->b_data, EXT4_I(inode)->i_data, ext_size); + /* zero out unused area in the extent block */ + memset(bh->b_data + ext_size, 0, inode->i_sb->s_blocksize - ext_size); /* set size of new block */ neh = ext_block_hdr(bh);