From 2cd4737bc850225de426a8dbee7a7a312a4f5304 Mon Sep 17 00:00:00 2001 From: Mimi Zohar Date: Tue, 30 Apr 2019 08:34:44 -0400 Subject: ima: prevent a file already mmap'ed write to be mmap'ed execute The kernel calls deny_write_access() to prevent a file already opened for write from being executed and also prevents files being executed from being opened for write. For some reason this does not extend to files being mmap'ed execute. From an IMA perspective, measuring/appraising the integrity of a file being mmap'ed shared execute, without first making sure the file cannot be modified, makes no sense. This patch prevents files, in policy, already mmap'ed shared write, from being mmap'ed execute. Signed-off-by: Mimi Zohar --- security/integrity/ima/ima_main.c | 32 ++++++++++++++++++++++++++++++-- 1 file changed, 30 insertions(+), 2 deletions(-) diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index 357edd140c09..f16353b5097e 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -72,6 +72,27 @@ out: } __setup("ima_hash=", hash_setup); +/* Prevent mmap'ing a file execute that is already mmap'ed write */ +static int mmap_violation_check(enum ima_hooks func, struct file *file, + char **pathbuf, const char **pathname, + char *filename) +{ + struct inode *inode; + int rc = 0; + + if ((func == MMAP_CHECK) && mapping_writably_mapped(file->f_mapping)) { + rc = -ETXTBSY; + inode = file_inode(file); + + if (!*pathbuf) /* ima_rdwr_violation possibly pre-fetched */ + *pathname = ima_d_path(&file->f_path, pathbuf, + filename); + integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, *pathname, + "mmap_file", "mmapped_writers", rc, 0); + } + return rc; +} + /* * ima_rdwr_violation_check * @@ -270,8 +291,12 @@ static int process_measurement(struct file *file, const struct cred *cred, /* Nothing to do, just return existing appraised status */ if (!action) { - if (must_appraise) - rc = ima_get_cache_status(iint, func); + if (must_appraise) { + rc = mmap_violation_check(func, file, &pathbuf, + &pathname, filename); + if (!rc) + rc = ima_get_cache_status(iint, func); + } goto out_locked; } @@ -298,6 +323,9 @@ static int process_measurement(struct file *file, const struct cred *cred, rc = ima_appraise_measurement(func, iint, file, pathname, xattr_value, xattr_len); inode_unlock(inode); + if (!rc) + rc = mmap_violation_check(func, file, &pathbuf, + &pathname, filename); } if (action & IMA_AUDIT) ima_audit_measurement(iint, pathname); -- cgit v1.2.3-55-g7522