From a311638793fa0b07ecbca079273288f7b143ab2a Mon Sep 17 00:00:00 2001 From: Mimi Zohar Date: Wed, 18 Oct 2023 14:47:02 -0400 Subject: [PATCH] ima: detect changes to the backing overlay file commit b836c4d29f2744200b2af41e14bf50758dddc818 upstream. Commit 18b44bc5a672 ("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 Tested-by: Eric Snowberg Tested-by: Raul E Rangel Cc: stable@vger.kernel.org Signed-off-by: Mimi Zohar Signed-off-by: Greg Kroah-Hartman --- fs/overlayfs/super.c | 2 +- security/integrity/ima/ima_api.c | 5 +++++ security/integrity/ima/ima_main.c | 16 +++++++++++++++- security/integrity/integrity.h | 2 ++ 4 files changed, 23 insertions(+), 2 deletions(-) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index 3fa2416..c71d185 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -1489,7 +1489,7 @@ int ovl_fill_super(struct super_block *sb, struct fs_context *fc) ovl_trusted_xattr_handlers; sb->s_fs_info = ofs; sb->s_flags |= SB_POSIXACL; - sb->s_iflags |= SB_I_SKIP_SYNC | SB_I_IMA_UNVERIFIABLE_SIGNATURE; + sb->s_iflags |= SB_I_SKIP_SYNC; err = -ENOMEM; root_dentry = ovl_get_root(sb, ctx->upper.dentry, oe); diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c index 452e80b..597ea0c 100644 --- a/security/integrity/ima/ima_api.c +++ b/security/integrity/ima/ima_api.c @@ -243,6 +243,7 @@ int ima_collect_measurement(struct integrity_iint_cache *iint, { const char *audit_cause = "failed"; struct inode *inode = file_inode(file); + struct inode *real_inode = d_real_inode(file_dentry(file)); const char *filename = file->f_path.dentry->d_name.name; struct ima_max_digest_data hash; struct kstat stat; @@ -302,6 +303,10 @@ int ima_collect_measurement(struct integrity_iint_cache *iint, iint->ima_hash = tmpbuf; memcpy(iint->ima_hash, &hash, length); iint->version = i_version; + if (real_inode != inode) { + iint->real_ino = real_inode->i_ino; + iint->real_dev = real_inode->i_sb->s_dev; + } /* Possibly temporary failure due to type of read (eg. O_DIRECT) */ if (!result) diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index 365db0e..cc1217a 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -25,6 +25,7 @@ #include #include #include +#include #include "ima.h" @@ -207,7 +208,7 @@ static int process_measurement(struct file *file, const struct cred *cred, u32 secid, char *buf, loff_t size, int mask, enum ima_hooks func) { - struct inode *inode = file_inode(file); + struct inode *backing_inode, *inode = file_inode(file); struct integrity_iint_cache *iint = NULL; struct ima_template_desc *template_desc = NULL; char *pathbuf = NULL; @@ -284,6 +285,19 @@ static int process_measurement(struct file *file, const struct cred *cred, iint->measured_pcrs = 0; } + /* Detect and re-evaluate changes made to the backing file. */ + backing_inode = d_real_inode(file_dentry(file)); + if (backing_inode != inode && + (action & IMA_DO_MASK) && (iint->flags & IMA_DONE_MASK)) { + if (!IS_I_VERSION(backing_inode) || + backing_inode->i_sb->s_dev != iint->real_dev || + backing_inode->i_ino != iint->real_ino || + !inode_eq_iversion(backing_inode, iint->version)) { + iint->flags &= ~IMA_DONE_MASK; + iint->measured_pcrs = 0; + } + } + /* Determine if already appraised/measured based on bitmask * (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED, * IMA_AUDIT, IMA_AUDITED) diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h index d7553c9..9561db7 100644 --- a/security/integrity/integrity.h +++ b/security/integrity/integrity.h @@ -164,6 +164,8 @@ struct integrity_iint_cache { unsigned long flags; unsigned long measured_pcrs; unsigned long atomic_flags; + unsigned long real_ino; + dev_t real_dev; enum integrity_status ima_file_status:4; enum integrity_status ima_mmap_status:4; enum integrity_status ima_bprm_status:4; -- 2.7.4