syscall: fix Getdirentries on 32-bit freebsd 12

On freebsd 12, the system call for getdirentries writes 64 bits to
*basep, even on 32-bit systems. Accomodate that by providing a uint64
to the system call and copy the base to/from that uint64.
The uint64 seems to be a virtual file offset, so failing if the high
bits are not zero should be fine for reasonable-sized directories.

Fixes #32498

Change-Id: Ie22c0d301c6091bd20e813432928b24ab95cc314
Reviewed-on: https://go-review.googlesource.com/c/go/+/181377
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

4 files changed, 19 insertions, 5 deletions

diff --git a/src/syscall/syscall_freebsd.go b/src/syscall/syscall_freebsd.go
index 87a27b1ff7..725fe51eb9 100644
--- a/src/syscall/syscall_freebsd.go
+++ b/src/syscall/syscall_freebsd.go
@@ -267,7 +267,21 @@ func Fstatfs(fd int, st *Statfs_t) (err error) {
 
 func Getdirentries(fd int, buf []byte, basep *uintptr) (n int, err error) {
 	if supportsABI(_ino64First) {
-		return getdirentries_freebsd12(fd, buf, basep)
+		if unsafe.Sizeof(*basep) == 64 {
+			return getdirentries_freebsd12(fd, buf, (*uint64)(unsafe.Pointer(basep)))
+		}
+		// The freebsd12 syscall needs a 64-bit base. On 32-bit machines
+		// we can't just use the basep passed in. See #32498.
+		var base uint64 = uint64(*basep)
+		n, err = getdirentries_freebsd12(fd, buf, &base)
+		*basep = uintptr(base)
+		if base>>32 != 0 {
+			// We can't stuff the base back into a uintptr, so any
+			// future calls would be suspect. Generate an error.
+			// EIO is allowed by getdirentries.
+			err = EIO
+		}
+		return
 	}
 
 	// The old syscall entries are smaller than the new. Use 1/4 of the original
@@ -424,7 +438,7 @@ func convertFromDirents11(buf []byte, old []byte) int {
 //sys	Fsync(fd int) (err error)
 //sys	Ftruncate(fd int, length int64) (err error)
 //sys	getdirentries(fd int, buf []byte, basep *uintptr) (n int, err error)
-//sys	getdirentries_freebsd12(fd int, buf []byte, basep *uintptr) (n int, err error) = _SYS_GETDIRENTRIES_FREEBSD12
+//sys	getdirentries_freebsd12(fd int, buf []byte, basep *uint64) (n int, err error) = _SYS_GETDIRENTRIES_FREEBSD12
 //sys	Getdtablesize() (size int)
 //sysnb	Getegid() (egid int)
 //sysnb	Geteuid() (uid int)
diff --git a/src/syscall/zsyscall_freebsd_386.go b/src/syscall/zsyscall_freebsd_386.go
index 8f4234c7e9..ddc265f190 100644
--- a/src/syscall/zsyscall_freebsd_386.go
+++ b/src/syscall/zsyscall_freebsd_386.go
@@ -570,7 +570,7 @@ func getdirentries(fd int, buf []byte, basep *uintptr) (n int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func getdirentries_freebsd12(fd int, buf []byte, basep *uintptr) (n int, err error) {
+func getdirentries_freebsd12(fd int, buf []byte, basep *uint64) (n int, err error) {
 	var _p0 unsafe.Pointer
 	if len(buf) > 0 {
 		_p0 = unsafe.Pointer(&buf[0])
diff --git a/src/syscall/zsyscall_freebsd_amd64.go b/src/syscall/zsyscall_freebsd_amd64.go
index baa7d68a7d..a0f79522b9 100644
--- a/src/syscall/zsyscall_freebsd_amd64.go
+++ b/src/syscall/zsyscall_freebsd_amd64.go
@@ -570,7 +570,7 @@ func getdirentries(fd int, buf []byte, basep *uintptr) (n int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func getdirentries_freebsd12(fd int, buf []byte, basep *uintptr) (n int, err error) {
+func getdirentries_freebsd12(fd int, buf []byte, basep *uint64) (n int, err error) {
 	var _p0 unsafe.Pointer
 	if len(buf) > 0 {
 		_p0 = unsafe.Pointer(&buf[0])
diff --git a/src/syscall/zsyscall_freebsd_arm.go b/src/syscall/zsyscall_freebsd_arm.go
index 16e4bc5414..2cd23d3db6 100644
--- a/src/syscall/zsyscall_freebsd_arm.go
+++ b/src/syscall/zsyscall_freebsd_arm.go
@@ -570,7 +570,7 @@ func getdirentries(fd int, buf []byte, basep *uintptr) (n int, err error) {
 
 // THIS FILE IS GENERATED BY THE COMMAND AT THE TOP; DO NOT EDIT
 
-func getdirentries_freebsd12(fd int, buf []byte, basep *uintptr) (n int, err error) {
+func getdirentries_freebsd12(fd int, buf []byte, basep *uint64) (n int, err error) {
 	var _p0 unsafe.Pointer
 	if len(buf) > 0 {
 		_p0 = unsafe.Pointer(&buf[0])