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Commit 70946c4a authored by Sascha Hauer's avatar Sascha Hauer Committed by Mimi Zohar
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evm: check for remount ro in progress before writing 



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: default avatarSascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: default avatarMimi Zohar <zohar@linux.vnet.ibm.com>
parent f5e51fa3

security/integrity/evm/evm_main.c

+6 −2
Original line number Diff line number Diff line
@@ -124,6 +124,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, 
	struct evm_ima_xattr_data *xattr_data = NULL;

	struct evm_ima_xattr_data calc;

	enum integrity_status evm_status = INTEGRITY_PASS;

	struct inode *inode;

	int rc, xattr_len;



	if (iint && (iint->evm_status == INTEGRITY_PASS ||
@@ -178,12 +179,15 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, 
					(const char *)xattr_data, xattr_len,

					calc.digest, sizeof(calc.digest));

		if (!rc) {

			inode = d_backing_inode(dentry);



			if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG) {

				if (iint)

					iint->flags |= EVM_IMMUTABLE_DIGSIG;

				evm_status = INTEGRITY_PASS_IMMUTABLE;

			} else if (!IS_RDONLY(d_backing_inode(dentry)) &&

				   !IS_IMMUTABLE(d_backing_inode(dentry))) {

			} else if (!IS_RDONLY(inode) &&

				   !(inode->i_sb->s_readonly_remount) &&

				   !IS_IMMUTABLE(inode)) {

				evm_update_evmxattr(dentry, xattr_name,

						    xattr_value,

						    xattr_value_len);