5.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Arnd Bergmann <arnd@xxxxxxxx>
commit 4b8e88e563b5f666446d002ad0dc1e6e8e7102b0 upstream.
The old ftruncate() syscall, using the 32-bit off_t misses a sign
extension when called in compat mode on 64-bit architectures. As a
result, passing a negative length accidentally succeeds in truncating
to file size between 2GiB and 4GiB.
Changing the type of the compat syscall to the signed compat_off_t
changes the behavior so it instead returns -EINVAL.
The native entry point, the truncate() syscall and the corresponding
loff_t based variants are all correct already and do not suffer
from this mistake.
Fixes: 3f6d078d4acc ("fix compat truncate/ftruncate")
Reviewed-by: Christian Brauner <brauner@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/open.c | 4 ++--
include/linux/compat.h | 2 +-
include/linux/syscalls.h | 2 +-
3 files changed, 4 insertions(+), 4 deletions(-)
--- a/fs/open.c
+++ b/fs/open.c
@@ -200,13 +200,13 @@ out:
return error;
}
-SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
+SYSCALL_DEFINE2(ftruncate, unsigned int, fd, off_t, length)
{
return do_sys_ftruncate(fd, length, 1);
}
#ifdef CONFIG_COMPAT
-COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_ulong_t, length)
+COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_off_t, length)
{
return do_sys_ftruncate(fd, length, 1);
}
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -527,7 +527,7 @@ asmlinkage long compat_sys_fstatfs(unsig
asmlinkage long compat_sys_fstatfs64(unsigned int fd, compat_size_t sz,
struct compat_statfs64 __user *buf);
asmlinkage long compat_sys_truncate(const char __user *, compat_off_t);
-asmlinkage long compat_sys_ftruncate(unsigned int, compat_ulong_t);
+asmlinkage long compat_sys_ftruncate(unsigned int, compat_off_t);
/* No generic prototype for truncate64, ftruncate64, fallocate */
asmlinkage long compat_sys_openat(int dfd, const char __user *filename,
int flags, umode_t mode);
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -445,7 +445,7 @@ asmlinkage long sys_fstatfs(unsigned int
asmlinkage long sys_fstatfs64(unsigned int fd, size_t sz,
struct statfs64 __user *buf);
asmlinkage long sys_truncate(const char __user *path, long length);
-asmlinkage long sys_ftruncate(unsigned int fd, unsigned long length);
+asmlinkage long sys_ftruncate(unsigned int fd, off_t length);
#if BITS_PER_LONG == 32
asmlinkage long sys_truncate64(const char __user *path, loff_t length);
asmlinkage long sys_ftruncate64(unsigned int fd, loff_t length);
