On Thu, 2018-03-01 at 13:38 +0100, Sascha Hauer wrote:
> EVM might update the evm xattr while the VFS performs a remount to
> readonly mode. This is not properly checked for, additionally check
> the s_readonly_remount superblock flag before writing.
> The bug can for example be observed with UBIFS. UBIFS checks the free
> space on the device before and after a remount. With EVM enabled the
> free space sometimes differs between both checks.
>
> Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
> ---
> security/integrity/evm/evm_main.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
> index a8d502827270..4a147a998aa7 100644
> --- a/security/integrity/evm/evm_main.c
> +++ b/security/integrity/evm/evm_main.c
> @@ -185,6 +185,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
> iint->flags |= EVM_IMMUTABLE_DIGSIG;
> evm_status = INTEGRITY_PASS_IMMUTABLE;
> } else if (!IS_RDONLY(d_backing_inode(dentry)) &&
> + !(dentry->d_inode->i_sb->s_readonly_remount) &&
The other 2 conditions are using d_back_inode(). Shouldn't this one
be too?
Mimi
> !IS_IMMUTABLE(d_backing_inode(dentry))) {
> evm_update_evmxattr(dentry, xattr_name,
> xattr_value,
