fs: fix archiecture-specific compat_ftruncate64

The "small" argument to do_sys_ftruncate indicates if > 32-bit size
should be reject, but all the arch-specific compat ftruncate64
implementations get this wrong.  Merge do_sys_ftruncate and
ksys_ftruncate, replace the integer as boolean small flag with a
descriptive one about LFS semantics, and use it correctly in the
architecture-specific ftruncate64 implementations.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Fixes: 3dd681d944 ("arm64: 32-bit (compat) applications support")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://patch.msgid.link/20260323070205.2939118-2-hch@lst.de
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

arch/arm64/kernel/sys32.c

@@ -89,7 +89,7 @@ COMPAT_SYSCALL_DEFINE4(aarch32_truncate64, const char __user *, pathname,
 COMPAT_SYSCALL_DEFINE4(aarch32_ftruncate64, unsigned int, fd, u32, __pad,
 		       arg_u32p(length))
 {
-	return ksys_ftruncate(fd, arg_u64(length));
+	return ksys_ftruncate(fd, arg_u64(length), FTRUNCATE_LFS);
 }
 
 COMPAT_SYSCALL_DEFINE5(aarch32_readahead, int, fd, u32, __pad,

arch/mips/kernel/linux32.c

@@ -60,7 +60,7 @@ SYSCALL_DEFINE4(32_truncate64, const char __user *, path,
 SYSCALL_DEFINE4(32_ftruncate64, unsigned long, fd, unsigned long, __dummy,
 	unsigned long, a2, unsigned long, a3)
 {
-	return ksys_ftruncate(fd, merge_64(a2, a3));
+	return ksys_ftruncate(fd, merge_64(a2, a3), FTRUNCATE_LFS);
 }
 
 SYSCALL_DEFINE5(32_llseek, unsigned int, fd, unsigned int, offset_high,

arch/parisc/kernel/sys_parisc.c

@@ -216,7 +216,7 @@ asmlinkage long parisc_truncate64(const char __user * path,
 asmlinkage long parisc_ftruncate64(unsigned int fd,
 					unsigned int high, unsigned int low)
 {
-	return ksys_ftruncate(fd, (long)high << 32 | low);
+	return ksys_ftruncate(fd, (long)high << 32 | low, FTRUNCATE_LFS);
 }
 
 /* stubs for the benefit of the syscall_table since truncate64 and truncate 
@@ -227,7 +227,7 @@ asmlinkage long sys_truncate64(const char __user * path, unsigned long length)
 }
 asmlinkage long sys_ftruncate64(unsigned int fd, unsigned long length)
 {
-	return ksys_ftruncate(fd, length);
+	return ksys_ftruncate(fd, length, FTRUNCATE_LFS);
 }
 asmlinkage long sys_fcntl64(unsigned int fd, unsigned int cmd, unsigned long arg)
 {

arch/powerpc/kernel/sys_ppc32.c

@@ -101,7 +101,7 @@ PPC32_SYSCALL_DEFINE4(ppc_ftruncate64,
 		       unsigned int, fd, u32, reg4,
 		       unsigned long, len1, unsigned long, len2)
 {
-	return ksys_ftruncate(fd, merge_64(len1, len2));
+	return ksys_ftruncate(fd, merge_64(len1, len2), FTRUNCATE_LFS);
 }
 
 PPC32_SYSCALL_DEFINE6(ppc32_fadvise64,

arch/sparc/kernel/sys_sparc32.c

@@ -58,7 +58,7 @@ COMPAT_SYSCALL_DEFINE3(truncate64, const char __user *, path, u32, high, u32, lo
 
 COMPAT_SYSCALL_DEFINE3(ftruncate64, unsigned int, fd, u32, high, u32, low)
 {
-	return ksys_ftruncate(fd, ((u64)high << 32) | low);
+	return ksys_ftruncate(fd, ((u64)high << 32) | low, FTRUNCATE_LFS);
 }
 
 static int cp_compat_stat64(struct kstat *stat,

arch/x86/kernel/sys_ia32.c

@@ -61,7 +61,8 @@ SYSCALL_DEFINE3(ia32_truncate64, const char __user *, filename,
 SYSCALL_DEFINE3(ia32_ftruncate64, unsigned int, fd,
 		unsigned long, offset_low, unsigned long, offset_high)
 {
-	return ksys_ftruncate(fd, ((loff_t) offset_high << 32) | offset_low);
+	return ksys_ftruncate(fd, ((loff_t) offset_high << 32) | offset_low,
+			FTRUNCATE_LFS);
 }
 
 /* warning: next two assume little endian */

fs/internal.h

@@ -199,7 +199,6 @@ extern int build_open_flags(const struct open_how *how, struct open_flags *op);
 struct file *file_close_fd_locked(struct files_struct *files, unsigned fd);
 
 int do_ftruncate(struct file *file, loff_t length, int small);
-int do_sys_ftruncate(unsigned int fd, loff_t length, int small);
 int chmod_common(const struct path *path, umode_t mode);
 int do_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group,
 		int flag);

fs/open.c

@@ -197,7 +197,7 @@ int do_ftruncate(struct file *file, loff_t length, int small)
 				   ATTR_MTIME | ATTR_CTIME, file);
 }
 
-int do_sys_ftruncate(unsigned int fd, loff_t length, int small)
+int ksys_ftruncate(unsigned int fd, loff_t length, unsigned int flags)
 {
 	if (length < 0)
 		return -EINVAL;
@@ -205,18 +205,18 @@ int do_sys_ftruncate(unsigned int fd, loff_t length, int small)
 	if (fd_empty(f))
 		return -EBADF;
 
-	return do_ftruncate(fd_file(f), length, small);
+	return do_ftruncate(fd_file(f), length, !(flags & FTRUNCATE_LFS));
 }
 
 SYSCALL_DEFINE2(ftruncate, unsigned int, fd, off_t, length)
 {
-	return do_sys_ftruncate(fd, length, 1);
+	return ksys_ftruncate(fd, length, 0);
 }
 
 #ifdef CONFIG_COMPAT
 COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_off_t, length)
 {
-	return do_sys_ftruncate(fd, length, 1);
+	return ksys_ftruncate(fd, length, 0);
 }
 #endif
 
@@ -229,7 +229,7 @@ SYSCALL_DEFINE2(truncate64, const char __user *, path, loff_t, length)
 
 SYSCALL_DEFINE2(ftruncate64, unsigned int, fd, loff_t, length)
 {
-	return do_sys_ftruncate(fd, length, 0);
+	return ksys_ftruncate(fd, length, FTRUNCATE_LFS);
 }
 #endif /* BITS_PER_LONG == 32 */
 
@@ -245,7 +245,7 @@ COMPAT_SYSCALL_DEFINE3(truncate64, const char __user *, pathname,
 COMPAT_SYSCALL_DEFINE3(ftruncate64, unsigned int, fd,
 		       compat_arg_u64_dual(length))
 {
-	return ksys_ftruncate(fd, compat_arg_u64_glue(length));
+	return ksys_ftruncate(fd, compat_arg_u64_glue(length), FTRUNCATE_LFS);
 }
 #endif
 

include/linux/syscalls.h

@@ -1283,12 +1283,8 @@ static inline long ksys_lchown(const char __user *filename, uid_t user,
 			     AT_SYMLINK_NOFOLLOW);
 }
 
-int do_sys_ftruncate(unsigned int fd, loff_t length, int small);
-
-static inline long ksys_ftruncate(unsigned int fd, loff_t length)
-{
-	return do_sys_ftruncate(fd, length, 1);
-}
+#define FTRUNCATE_LFS	(1u << 0)	/* allow truncating > 32-bit */
+int ksys_ftruncate(unsigned int fd, loff_t length, unsigned int flags);
 
 int do_sys_truncate(const char __user *pathname, loff_t length);