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ima: detect changes to the backing overlay file
commitb836c4d29f
upstream. Commit18b44bc5a6
("ovl: Always reevaluate the file signature for IMA") forced signature re-evaulation on every file access. Instead of always re-evaluating the file's integrity, detect a change to the backing file, by comparing the cached file metadata with the backing file's metadata. Verifying just the i_version has not changed is insufficient. In addition save and compare the i_ino and s_dev as well. Reviewed-by: Amir Goldstein <amir73il@gmail.com> Tested-by: Eric Snowberg <eric.snowberg@oracle.com> Tested-by: Raul E Rangel <rrangel@chromium.org> Cc: stable@vger.kernel.org Signed-off-by: Mimi Zohar <zohar@linux.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -1467,7 +1467,7 @@ int ovl_fill_super(struct super_block *sb, struct fs_context *fc)
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ovl_trusted_xattr_handlers;
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sb->s_fs_info = ofs;
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sb->s_flags |= SB_POSIXACL;
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sb->s_iflags |= SB_I_SKIP_SYNC | SB_I_IMA_UNVERIFIABLE_SIGNATURE;
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sb->s_iflags |= SB_I_SKIP_SYNC;
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err = -ENOMEM;
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root_dentry = ovl_get_root(sb, ctx->upper.dentry, oe);
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@ -243,6 +243,7 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
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{
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const char *audit_cause = "failed";
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struct inode *inode = file_inode(file);
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struct inode *real_inode = d_real_inode(file_dentry(file));
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const char *filename = file->f_path.dentry->d_name.name;
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struct ima_max_digest_data hash;
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struct kstat stat;
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@ -302,6 +303,10 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
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iint->ima_hash = tmpbuf;
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memcpy(iint->ima_hash, &hash, length);
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iint->version = i_version;
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if (real_inode != inode) {
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iint->real_ino = real_inode->i_ino;
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iint->real_dev = real_inode->i_sb->s_dev;
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}
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/* Possibly temporary failure due to type of read (eg. O_DIRECT) */
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if (!result)
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@ -25,6 +25,7 @@
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#include <linux/xattr.h>
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#include <linux/ima.h>
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#include <linux/fs.h>
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#include <linux/iversion.h>
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#include "ima.h"
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@ -207,7 +208,7 @@ static int process_measurement(struct file *file, const struct cred *cred,
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u32 secid, char *buf, loff_t size, int mask,
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enum ima_hooks func)
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{
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struct inode *inode = file_inode(file);
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struct inode *backing_inode, *inode = file_inode(file);
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struct integrity_iint_cache *iint = NULL;
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struct ima_template_desc *template_desc = NULL;
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char *pathbuf = NULL;
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@ -284,6 +285,19 @@ static int process_measurement(struct file *file, const struct cred *cred,
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iint->measured_pcrs = 0;
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}
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/* Detect and re-evaluate changes made to the backing file. */
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backing_inode = d_real_inode(file_dentry(file));
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if (backing_inode != inode &&
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(action & IMA_DO_MASK) && (iint->flags & IMA_DONE_MASK)) {
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if (!IS_I_VERSION(backing_inode) ||
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backing_inode->i_sb->s_dev != iint->real_dev ||
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backing_inode->i_ino != iint->real_ino ||
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!inode_eq_iversion(backing_inode, iint->version)) {
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iint->flags &= ~IMA_DONE_MASK;
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iint->measured_pcrs = 0;
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}
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}
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/* Determine if already appraised/measured based on bitmask
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* (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
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* IMA_AUDIT, IMA_AUDITED)
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@ -164,6 +164,8 @@ struct integrity_iint_cache {
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unsigned long flags;
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unsigned long measured_pcrs;
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unsigned long atomic_flags;
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unsigned long real_ino;
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dev_t real_dev;
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enum integrity_status ima_file_status:4;
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enum integrity_status ima_mmap_status:4;
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enum integrity_status ima_bprm_status:4;
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