From: Scott Branden <scott.branden@xxxxxxxxxxxx> When the kernel_read_file LSM hook is called with contents=false, IMA can appraise the file directly, without requiring a filled buffer. When such a buffer is available, though, IMA can continue to use it instead of forcing a double read here. Signed-off-by: Scott Branden <scott.branden@xxxxxxxxxxxx> Link: https://lore.kernel.org/lkml/20200706232309.12010-10-scott.branden@xxxxxxxxxxxx/ Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Reviewed-by: Mimi Zohar <zohar@xxxxxxxxxxxxx> --- security/integrity/ima/ima_main.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index 939f53d02627..82c9d62bcb11 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -613,11 +613,8 @@ void ima_post_path_mknod(struct dentry *dentry) int ima_read_file(struct file *file, enum kernel_read_file_id read_id, bool contents) { - /* Reject all partial reads during appraisal. */ - if (!contents) { - if (ima_appraise & IMA_APPRAISE_ENFORCE) - return -EACCES; - } + enum ima_hooks func; + u32 secid; /* * Do devices using pre-allocated memory run the risk of the @@ -626,7 +623,20 @@ int ima_read_file(struct file *file, enum kernel_read_file_id read_id, * buffers? It may be desirable to include the buffer address * in this API and walk all the dma_map_single() mappings to check. */ - return 0; + + /* + * There will be a call made to ima_post_read_file() with + * a filled buffer, so we don't need to perform an extra + * read early here. + */ + if (contents) + return 0; + + /* Read entire file for all partial reads. */ + func = read_idmap[read_id] ?: FILE_CHECK; + security_task_getsecid(current, &secid); + return process_measurement(file, current_cred(), secid, NULL, + 0, MAY_READ, func); } const int read_idmap[READING_MAX_ID] = { -- 2.25.1
