[PATCH 06/16] um: ubd: use 64-bit time_t where possible

Arnd Bergmann
2019-11-08T21:35:49Z

The ubd code suffers from a possible y2038 overflow on 32-bit
architectures, both for the cow header and the os_file_modtime()
function.

Replace time_t with time64_t to extend the ubd_kern side as much
as possible.

Whether this makes a difference for the user side depends on
the host libc implementation that may use either 32-bit or 64-bit
time_t.

For the cow file format, the header contains an unsigned 32-bit
timestamp, which is good until y2106, passing this through a
'long long' gives us a consistent interpretation between 32-bit
and 64-bit um kernels.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
arch/um/drivers/cow.h | 2 +-
arch/um/drivers/cow_user.c | 7 ++++---
arch/um/drivers/ubd_kern.c | 10 +++++-----
arch/um/include/shared/os.h | 2 +-
arch/um/os-Linux/file.c | 2 +-
5 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/arch/um/drivers/cow.h b/arch/um/drivers/cow.h
index 760c507dd5b6..103adac691ed 100644
--- a/arch/um/drivers/cow.h
+++ b/arch/um/drivers/cow.h
@@ -11,7 +11,7 @@ extern int init_cow_file(int fd, char *cow_file, char *backing_file,
extern int file_reader(__u64 offset, char *buf, int len, void *arg);
extern int read_cow_header(int (*reader)(__u64, char *, int, void *),
void *arg, __u32 *version_out,
- char **backing_file_out, time_t *mtime_out,
+ char **backing_file_out, long long *mtime_out,
unsigned long long *size_out, int *sectorsize_out,
__u32 *align_out, int *bitmap_offset_out);

diff --git a/arch/um/drivers/cow_user.c b/arch/um/drivers/cow_user.c
index 74b0c2686c95..29b46581ddd1 100644
--- a/arch/um/drivers/cow_user.c
+++ b/arch/um/drivers/cow_user.c
@@ -17,6 +17,7 @@

#define PATH_LEN_V1 256

+/* unsigned time_t works until year 2106 */
typedef __u32 time32_t;

struct cow_header_v1 {
@@ -197,7 +198,7 @@ int write_cow_header(char *cow_file, int fd, char *backing_file,
int sectorsize, int alignment, unsigned long long *size)
{
struct cow_header_v3 *header;
- unsigned long modtime;
+ long long modtime;
int err;

err = cow_seek_file(fd, 0);
@@ -276,7 +277,7 @@ int file_reader(__u64 offset, char *buf, int len, void *arg)

int read_cow_header(int (*reader)(__u64, char *, int, void *), void *arg,
__u32 *version_out, char **backing_file_out,
- time_t *mtime_out, unsigned long long *size_out,
+ long long *mtime_out, unsigned long long *size_out,
int *sectorsize_out, __u32 *align_out,
int *bitmap_offset_out)
{
@@ -363,7 +364,7 @@ int read_cow_header(int (*reader)(__u64, char *, int, void *), void *arg,

/*
* this was used until Dec2005 - 64bits are needed to represent
- * 2038+. I.e. we can safely do this truncating cast.
+ * 2106+. I.e. we can safely do this truncating cast.
*
* Additionally, we must use be32toh() instead of be64toh(), since
* the program used to use the former (tested - I got mtime
diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
index 6627d7c30f37..dcabb463e011 100644
--- a/arch/um/drivers/ubd_kern.c
+++ b/arch/um/drivers/ubd_kern.c
@@ -561,7 +561,7 @@ static inline int ubd_file_size(struct ubd *ubd_dev, __u64 *size_out)
__u32 version;
__u32 align;
char *backing_file;
- time_t mtime;
+ time64_t mtime;
unsigned long long size;
int sector_size;
int bitmap_offset;
@@ -600,9 +600,9 @@ static int read_cow_bitmap(int fd, void *buf, int offset, int len)
return 0;
}

-static int backing_file_mismatch(char *file, __u64 size, time_t mtime)
+static int backing_file_mismatch(char *file, __u64 size, time64_t mtime)
{
- unsigned long modtime;
+ time64_t modtime;
unsigned long long actual;
int err;

@@ -628,7 +628,7 @@ static int backing_file_mismatch(char *file, __u64 size, time_t mtime)
return -EINVAL;
}
if (modtime != mtime) {
- printk(KERN_ERR "mtime mismatch (%ld vs %ld) of COW header vs "
+ printk(KERN_ERR "mtime mismatch (%lld vs %lld) of COW header vs "
"backing file\n", mtime, modtime);
return -EINVAL;
}
@@ -671,7 +671,7 @@ static int open_ubd_file(char *file, struct openflags *openflags, int shared,
unsigned long *bitmap_len_out, int *data_offset_out,
int *create_cow_out)
{
- time_t mtime;
+ time64_t mtime;
unsigned long long size;
__u32 version, align;
char *backing_file;
diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 506bcd1bca68..0f30204b6afa 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -150,7 +150,7 @@ extern int os_sync_file(int fd);
extern int os_file_size(const char *file, unsigned long long *size_out);
extern int os_pread_file(int fd, void *buf, int len, unsigned long long offset);
extern int os_pwrite_file(int fd, const void *buf, int count, unsigned long long offset);
-extern int os_file_modtime(const char *file, unsigned long *modtime);
+extern int os_file_modtime(const char *file, long long *modtime);
extern int os_pipe(int *fd, int stream, int close_on_exec);
extern int os_set_fd_async(int fd);
extern int os_clear_fd_async(int fd);
diff --git a/arch/um/os-Linux/file.c b/arch/um/os-Linux/file.c
index 5133e3afb96f..fbda10535dab 100644
--- a/arch/um/os-Linux/file.c
+++ b/arch/um/os-Linux/file.c
@@ -341,7 +341,7 @@ int os_file_size(const char *file, unsigned long long *size_out)
return 0;
}

-int os_file_modtime(const char *file, unsigned long *modtime)
+int os_file_modtime(const char *file, long long *modtime)
{
struct uml_stat buf;
int err;
--
2.20.0