[PATCH v2 08/18] fs/kernel_read_file: Remove redundant size argument

Kees Cook
2020-07-22T19:39:22Z

In preparation for refactoring kernel_read_file*(), remove the redundant
"size" argument which is not needed: it can be included in the return
code, with callers adjusted. (VFS reads already cannot be larger than
INT_MAX.)

Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/base/firmware_loader/main.c | 10 ++++++----
fs/kernel_read_file.c | 20 +++++++++-----------
include/linux/kernel_read_file.h | 8 ++++----
kernel/kexec_file.c | 14 +++++++-------
kernel/module.c | 7 +++----
security/integrity/digsig.c | 5 +++--
security/integrity/ima/ima_fs.c | 6 ++++--
7 files changed, 36 insertions(+), 34 deletions(-)

diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c
index d4a413ea48ce..f80c0d102be8 100644
--- a/drivers/base/firmware_loader/main.c
+++ b/drivers/base/firmware_loader/main.c
@@ -462,7 +462,7 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
size_t in_size,
const void *in_buffer))
{
- loff_t size;
+ size_t size;
int i, len;
int rc = -ENOENT;
char *path;
@@ -494,10 +494,9 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
fw_priv->size = 0;

/* load firmware files from the mount namespace of init */
- rc = kernel_read_file_from_path_initns(path, &buffer,
- &size, msize,
+ rc = kernel_read_file_from_path_initns(path, &buffer, msize,
READING_FIRMWARE);
- if (rc) {
+ if (rc < 0) {
if (rc != -ENOENT)
dev_warn(device, "loading %s failed with error %d\n",
path, rc);
@@ -506,6 +505,9 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
path);
continue;
}
+ size = rc;
+ rc = 0;
+
dev_dbg(device, "Loading firmware from %s\n", path);
if (decompress) {
dev_dbg(device, "f/w decompressing %s\n",
diff --git a/fs/kernel_read_file.c b/fs/kernel_read_file.c
index 54d972d4befc..dc28a8def597 100644
--- a/fs/kernel_read_file.c
+++ b/fs/kernel_read_file.c
@@ -5,7 +5,7 @@
#include <linux/security.h>
#include <linux/vmalloc.h>

-int kernel_read_file(struct file *file, void **buf, loff_t *size,
+int kernel_read_file(struct file *file, void **buf,
loff_t max_size, enum kernel_read_file_id id)
{
loff_t i_size, pos;
@@ -29,7 +29,7 @@ int kernel_read_file(struct file *file, void **buf, loff_t *size,
ret = -EINVAL;
goto out;
}
- if (i_size > SIZE_MAX || (max_size > 0 && i_size > max_size)) {
+ if (i_size > INT_MAX || (max_size > 0 && i_size > max_size)) {
ret = -EFBIG;
goto out;
}
@@ -59,8 +59,6 @@ int kernel_read_file(struct file *file, void **buf, loff_t *size,
}

ret = security_kernel_post_read_file(file, *buf, i_size, id);
- if (!ret)
- *size = pos;

out_free:
if (ret < 0) {
@@ -72,11 +70,11 @@ int kernel_read_file(struct file *file, void **buf, loff_t *size,

out:
allow_write_access(file);
- return ret;
+ return ret == 0 ? pos : ret;
}
EXPORT_SYMBOL_GPL(kernel_read_file);

-int kernel_read_file_from_path(const char *path, void **buf, loff_t *size,
+int kernel_read_file_from_path(const char *path, void **buf,
loff_t max_size, enum kernel_read_file_id id)
{
struct file *file;
@@ -89,14 +87,14 @@ int kernel_read_file_from_path(const char *path, void **buf, loff_t *size,
if (IS_ERR(file))
return PTR_ERR(file);

- ret = kernel_read_file(file, buf, size, max_size, id);
+ ret = kernel_read_file(file, buf, max_size, id);
fput(file);
return ret;
}
EXPORT_SYMBOL_GPL(kernel_read_file_from_path);

int kernel_read_file_from_path_initns(const char *path, void **buf,
- loff_t *size, loff_t max_size,
+ loff_t max_size,
enum kernel_read_file_id id)
{
struct file *file;
@@ -115,13 +113,13 @@ int kernel_read_file_from_path_initns(const char *path, void **buf,
if (IS_ERR(file))
return PTR_ERR(file);

- ret = kernel_read_file(file, buf, size, max_size, id);
+ ret = kernel_read_file(file, buf, max_size, id);
fput(file);
return ret;
}
EXPORT_SYMBOL_GPL(kernel_read_file_from_path_initns);

-int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size,
+int kernel_read_file_from_fd(int fd, void **buf, loff_t max_size,
enum kernel_read_file_id id)
{
struct fd f = fdget(fd);
@@ -130,7 +128,7 @@ int kernel_read_file_from_fd(int fd, void **buf, loff_t *size, loff_t max_size,
if (!f.file)
goto out;

- ret = kernel_read_file(f.file, buf, size, max_size, id);
+ ret = kernel_read_file(f.file, buf, max_size, id);
out:
fdput(f);
return ret;
diff --git a/include/linux/kernel_read_file.h b/include/linux/kernel_read_file.h
index 78cf3d7dc835..0ca0bdbed1bd 100644
--- a/include/linux/kernel_read_file.h
+++ b/include/linux/kernel_read_file.h
@@ -36,16 +36,16 @@ static inline const char *kernel_read_file_id_str(enum kernel_read_file_id id)
}

int kernel_read_file(struct file *file,
- void **buf, loff_t *size, loff_t max_size,
+ void **buf, loff_t max_size,
enum kernel_read_file_id id);
int kernel_read_file_from_path(const char *path,
- void **buf, loff_t *size, loff_t max_size,
+ void **buf, loff_t max_size,
enum kernel_read_file_id id);
int kernel_read_file_from_path_initns(const char *path,
- void **buf, loff_t *size, loff_t max_size,
+ void **buf, loff_t max_size,
enum kernel_read_file_id id);
int kernel_read_file_from_fd(int fd,
- void **buf, loff_t *size, loff_t max_size,
+ void **buf, loff_t max_size,
enum kernel_read_file_id id);

#endif /* _LINUX_KERNEL_READ_FILE_H */
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 1358069ce9e9..eda19ca256a3 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -220,13 +220,12 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
{
int ret;
void *ldata;
- loff_t size;

ret = kernel_read_file_from_fd(kernel_fd, &image->kernel_buf,
- &size, INT_MAX, READING_KEXEC_IMAGE);
- if (ret)
+ INT_MAX, READING_KEXEC_IMAGE);
+ if (ret < 0)
return ret;
- image->kernel_buf_len = size;
+ image->kernel_buf_len = ret;

/* Call arch image probe handlers */
ret = arch_kexec_kernel_image_probe(image, image->kernel_buf,
@@ -243,11 +242,12 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
/* It is possible that there no initramfs is being loaded */
if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
ret = kernel_read_file_from_fd(initrd_fd, &image->initrd_buf,
- &size, INT_MAX,
+ INT_MAX,
READING_KEXEC_INITRAMFS);
- if (ret)
+ if (ret < 0)
goto out;
- image->initrd_buf_len = size;
+ image->initrd_buf_len = ret;
+ ret = 0;
}

if (cmdline_len) {
diff --git a/kernel/module.c b/kernel/module.c
index e9765803601b..b6fd4f51cc30 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3988,7 +3988,6 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags)
{
struct load_info info = { };
- loff_t size;
void *hdr = NULL;
int err;

@@ -4002,12 +4001,12 @@ SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags)
|MODULE_INIT_IGNORE_VERMAGIC))
return -EINVAL;

- err = kernel_read_file_from_fd(fd, &hdr, &size, INT_MAX,
+ err = kernel_read_file_from_fd(fd, &hdr, INT_MAX,
READING_MODULE);
- if (err)
+ if (err < 0)
return err;
info.hdr = hdr;
- info.len = size;
+ info.len = err;

return load_module(&info, uargs, flags);
}
diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
index f8869be45d8f..97661ffabc4e 100644
--- a/security/integrity/digsig.c
+++ b/security/integrity/digsig.c
@@ -171,16 +171,17 @@ int __init integrity_add_key(const unsigned int id, const void *data,
int __init integrity_load_x509(const unsigned int id, const char *path)
{
void *data = NULL;
- loff_t size;
+ size_t size;
int rc;
key_perm_t perm;

- rc = kernel_read_file_from_path(path, &data, &size, 0,
+ rc = kernel_read_file_from_path(path, &data, 0,
READING_X509_CERTIFICATE);
if (rc < 0) {
pr_err("Unable to open file: %s (%d)", path, rc);
return rc;
}
+ size = rc;

perm = (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW | KEY_USR_READ;

diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index e13ffece3726..602f52717757 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -275,7 +275,7 @@ static ssize_t ima_read_policy(char *path)
{
void *data = NULL;
char *datap;
- loff_t size;
+ size_t size;
int rc, pathlen = strlen(path);

char *p;
@@ -284,11 +284,13 @@ static ssize_t ima_read_policy(char *path)
datap = path;
strsep(&datap, "\n");

- rc = kernel_read_file_from_path(path, &data, &size, 0, READING_POLICY);
+ rc = kernel_read_file_from_path(path, &data, 0, READING_POLICY);
if (rc < 0) {
pr_err("Unable to open file: %s (%d)", path, rc);
return rc;
}
+ size = rc;
+ rc = 0;

datap = data;
while (size > 0 && (p = strsep(&datap, "\n"))) {