5.4-stable review patch. If anyone has any objections, please let me know.
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From: Phillip Lougher phillip@squashfs.org.uk
commit 74058c0a9fc8b2b4d5f4a0ef7ee2cfa66a9e49cf upstream.
Syzkaller reports a "KMSAN: uninit-value in squashfs_get_parent" bug.
This is caused by open_by_handle_at() being called with a file handle containing an invalid parent inode number. In particular the inode number is that of a symbolic link, rather than a directory.
Squashfs_get_parent() gets called with that symbolic link inode, and accesses the parent member field.
unsigned int parent_ino = squashfs_i(inode)->parent;
Because non-directory inodes in Squashfs do not have a parent value, this is uninitialised, and this causes an uninitialised value access.
The fix is to initialise parent with the invalid inode 0, which will cause an EINVAL error to be returned.
Regular inodes used to share the parent field with the block_list_start field. This is removed in this commit to enable the parent field to contain the invalid inode number 0.
Link: https://lkml.kernel.org/r/20250918233308.293861-1-phillip@squashfs.org.uk Fixes: 122601408d20 ("Squashfs: export operations") Signed-off-by: Phillip Lougher phillip@squashfs.org.uk Reported-by: syzbot+157bdef5cf596ad0da2c@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/68cc2431.050a0220.139b6.0001.GAE@google.com/ Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/squashfs/inode.c | 7 +++++++ fs/squashfs/squashfs_fs_i.h | 2 +- 2 files changed, 8 insertions(+), 1 deletion(-)
--- a/fs/squashfs/inode.c +++ b/fs/squashfs/inode.c @@ -165,6 +165,7 @@ int squashfs_read_inode(struct inode *in squashfs_i(inode)->start = le32_to_cpu(sqsh_ino->start_block); squashfs_i(inode)->block_list_start = block; squashfs_i(inode)->offset = offset; + squashfs_i(inode)->parent = 0; inode->i_data.a_ops = &squashfs_aops;
TRACE("File inode %x:%x, start_block %llx, block_list_start " @@ -212,6 +213,7 @@ int squashfs_read_inode(struct inode *in squashfs_i(inode)->start = le64_to_cpu(sqsh_ino->start_block); squashfs_i(inode)->block_list_start = block; squashfs_i(inode)->offset = offset; + squashfs_i(inode)->parent = 0; inode->i_data.a_ops = &squashfs_aops;
TRACE("File inode %x:%x, start_block %llx, block_list_start " @@ -292,6 +294,7 @@ int squashfs_read_inode(struct inode *in inode->i_mode |= S_IFLNK; squashfs_i(inode)->start = block; squashfs_i(inode)->offset = offset; + squashfs_i(inode)->parent = 0;
if (type == SQUASHFS_LSYMLINK_TYPE) { __le32 xattr; @@ -329,6 +332,7 @@ int squashfs_read_inode(struct inode *in set_nlink(inode, le32_to_cpu(sqsh_ino->nlink)); rdev = le32_to_cpu(sqsh_ino->rdev); init_special_inode(inode, inode->i_mode, new_decode_dev(rdev)); + squashfs_i(inode)->parent = 0;
TRACE("Device inode %x:%x, rdev %x\n", SQUASHFS_INODE_BLK(ino), offset, rdev); @@ -353,6 +357,7 @@ int squashfs_read_inode(struct inode *in set_nlink(inode, le32_to_cpu(sqsh_ino->nlink)); rdev = le32_to_cpu(sqsh_ino->rdev); init_special_inode(inode, inode->i_mode, new_decode_dev(rdev)); + squashfs_i(inode)->parent = 0;
TRACE("Device inode %x:%x, rdev %x\n", SQUASHFS_INODE_BLK(ino), offset, rdev); @@ -373,6 +378,7 @@ int squashfs_read_inode(struct inode *in inode->i_mode |= S_IFSOCK; set_nlink(inode, le32_to_cpu(sqsh_ino->nlink)); init_special_inode(inode, inode->i_mode, 0); + squashfs_i(inode)->parent = 0; break; } case SQUASHFS_LFIFO_TYPE: @@ -392,6 +398,7 @@ int squashfs_read_inode(struct inode *in inode->i_op = &squashfs_inode_ops; set_nlink(inode, le32_to_cpu(sqsh_ino->nlink)); init_special_inode(inode, inode->i_mode, 0); + squashfs_i(inode)->parent = 0; break; } default: --- a/fs/squashfs/squashfs_fs_i.h +++ b/fs/squashfs/squashfs_fs_i.h @@ -16,6 +16,7 @@ struct squashfs_inode_info { u64 xattr; unsigned int xattr_size; int xattr_count; + int parent; union { struct { u64 fragment_block; @@ -27,7 +28,6 @@ struct squashfs_inode_info { u64 dir_idx_start; int dir_idx_offset; int dir_idx_cnt; - int parent; }; }; struct inode vfs_inode;