From 07f258497932e53f4651b80a086117ffda843fe3 Mon Sep 17 00:00:00 2001 From: Dean Deng Date: Thu, 16 Jan 2020 12:33:07 -0800 Subject: Plumb getting/setting xattrs through InodeOperations and 9p gofer interfaces. There was a very bare get/setxattr in the InodeOperations interface. Add context.Context to both, size to getxattr, and flags to setxattr. Note that extended attributes are passed around as strings in this implementation, so size is automatically encoded into the value. Size is added in getxattr so that implementations can return ERANGE if a value is larger than can fit in the user-allocated buffer. This prevents us from unnecessarily passing around an arbitrarily large xattr when the user buffer is actually too small. Don't use the existing xattrwalk and xattrcreate messages and define our own, mainly for the sake of simplicity. Extended attributes will be implemented in future commits. PiperOrigin-RevId: 290121300 --- pkg/sentry/syscalls/linux/linux64_amd64.go | 4 +-- pkg/sentry/syscalls/linux/linux64_arm64.go | 4 +-- pkg/sentry/syscalls/linux/sys_xattr.go | 48 +++++++++++++++++------------- 3 files changed, 31 insertions(+), 25 deletions(-) (limited to 'pkg/sentry/syscalls/linux') diff --git a/pkg/sentry/syscalls/linux/linux64_amd64.go b/pkg/sentry/syscalls/linux/linux64_amd64.go index 479c5f6ff..6b2920900 100644 --- a/pkg/sentry/syscalls/linux/linux64_amd64.go +++ b/pkg/sentry/syscalls/linux/linux64_amd64.go @@ -228,10 +228,10 @@ var AMD64 = &kernel.SyscallTable{ 185: syscalls.Error("security", syserror.ENOSYS, "Not implemented in Linux.", nil), 186: syscalls.Supported("gettid", Gettid), 187: syscalls.Supported("readahead", Readahead), - 188: syscalls.PartiallySupported("setxattr", Setxattr, "Only supported for tmpfs.", nil), + 188: syscalls.PartiallySupported("setxattr", SetXattr, "Only supported for tmpfs.", nil), 189: syscalls.Error("lsetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), 190: syscalls.Error("fsetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), - 191: syscalls.PartiallySupported("getxattr", Getxattr, "Only supported for tmpfs.", nil), + 191: syscalls.PartiallySupported("getxattr", GetXattr, "Only supported for tmpfs.", nil), 192: syscalls.ErrorWithEvent("lgetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), 193: syscalls.ErrorWithEvent("fgetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), 194: syscalls.ErrorWithEvent("listxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), diff --git a/pkg/sentry/syscalls/linux/linux64_arm64.go b/pkg/sentry/syscalls/linux/linux64_arm64.go index d3f61f5e8..8c1b20911 100644 --- a/pkg/sentry/syscalls/linux/linux64_arm64.go +++ b/pkg/sentry/syscalls/linux/linux64_arm64.go @@ -41,10 +41,10 @@ var ARM64 = &kernel.SyscallTable{ 2: syscalls.PartiallySupported("io_submit", IoSubmit, "Generally supported with exceptions. User ring optimizations are not implemented.", []string{"gvisor.dev/issue/204"}), 3: syscalls.PartiallySupported("io_cancel", IoCancel, "Generally supported with exceptions. User ring optimizations are not implemented.", []string{"gvisor.dev/issue/204"}), 4: syscalls.PartiallySupported("io_getevents", IoGetevents, "Generally supported with exceptions. User ring optimizations are not implemented.", []string{"gvisor.dev/issue/204"}), - 5: syscalls.PartiallySupported("setxattr", Setxattr, "Only supported for tmpfs.", nil), + 5: syscalls.PartiallySupported("setxattr", SetXattr, "Only supported for tmpfs.", nil), 6: syscalls.Error("lsetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), 7: syscalls.Error("fsetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), - 8: syscalls.PartiallySupported("getxattr", Getxattr, "Only supported for tmpfs.", nil), + 8: syscalls.PartiallySupported("getxattr", GetXattr, "Only supported for tmpfs.", nil), 9: syscalls.ErrorWithEvent("lgetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), 10: syscalls.ErrorWithEvent("fgetxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), 11: syscalls.ErrorWithEvent("listxattr", syserror.ENOTSUP, "Requires filesystem support.", nil), diff --git a/pkg/sentry/syscalls/linux/sys_xattr.go b/pkg/sentry/syscalls/linux/sys_xattr.go index 97d9a65ea..816352218 100644 --- a/pkg/sentry/syscalls/linux/sys_xattr.go +++ b/pkg/sentry/syscalls/linux/sys_xattr.go @@ -25,12 +25,12 @@ import ( "gvisor.dev/gvisor/pkg/syserror" ) -// Getxattr implements linux syscall getxattr(2). -func Getxattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) { +// GetXattr implements linux syscall getxattr(2). +func GetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) { pathAddr := args[0].Pointer() nameAddr := args[1].Pointer() valueAddr := args[2].Pointer() - size := args[3].SizeT() + size := uint64(args[3].SizeT()) path, dirPath, err := copyInPath(t, pathAddr, false /* allowEmpty */) if err != nil { @@ -39,22 +39,28 @@ func Getxattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc valueLen := 0 err = fileOpOn(t, linux.AT_FDCWD, path, true /* resolve */, func(root *fs.Dirent, d *fs.Dirent, _ uint) error { - value, err := getxattr(t, d, dirPath, nameAddr) + // If getxattr(2) is called with size 0, the size of the value will be + // returned successfully even if it is nonzero. In that case, we need to + // retrieve the entire attribute value so we can return the correct size. + requestedSize := size + if size == 0 || size > linux.XATTR_SIZE_MAX { + requestedSize = linux.XATTR_SIZE_MAX + } + + value, err := getXattr(t, d, dirPath, nameAddr, uint64(requestedSize)) if err != nil { return err } valueLen = len(value) - if size == 0 { - return nil - } - if size > linux.XATTR_SIZE_MAX { - size = linux.XATTR_SIZE_MAX - } - if valueLen > int(size) { + if uint64(valueLen) > requestedSize { return syserror.ERANGE } + // Skip copying out the attribute value if size is 0. + if size == 0 { + return nil + } _, err = t.CopyOutBytes(valueAddr, []byte(value)) return err }) @@ -64,8 +70,8 @@ func Getxattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc return uintptr(valueLen), nil, nil } -// getxattr implements getxattr from the given *fs.Dirent. -func getxattr(t *kernel.Task, d *fs.Dirent, dirPath bool, nameAddr usermem.Addr) (string, error) { +// getXattr implements getxattr(2) from the given *fs.Dirent. +func getXattr(t *kernel.Task, d *fs.Dirent, dirPath bool, nameAddr usermem.Addr, size uint64) (string, error) { if dirPath && !fs.IsDir(d.Inode.StableAttr) { return "", syserror.ENOTDIR } @@ -83,15 +89,15 @@ func getxattr(t *kernel.Task, d *fs.Dirent, dirPath bool, nameAddr usermem.Addr) return "", syserror.EOPNOTSUPP } - return d.Inode.Getxattr(name) + return d.Inode.GetXattr(t, name, size) } -// Setxattr implements linux syscall setxattr(2). -func Setxattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) { +// SetXattr implements linux syscall setxattr(2). +func SetXattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) { pathAddr := args[0].Pointer() nameAddr := args[1].Pointer() valueAddr := args[2].Pointer() - size := args[3].SizeT() + size := uint64(args[3].SizeT()) flags := args[4].Uint() path, dirPath, err := copyInPath(t, pathAddr, false /* allowEmpty */) @@ -104,12 +110,12 @@ func Setxattr(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sysc } return 0, nil, fileOpOn(t, linux.AT_FDCWD, path, true /* resolve */, func(root *fs.Dirent, d *fs.Dirent, _ uint) error { - return setxattr(t, d, dirPath, nameAddr, valueAddr, size, flags) + return setXattr(t, d, dirPath, nameAddr, valueAddr, uint64(size), flags) }) } -// setxattr implements setxattr from the given *fs.Dirent. -func setxattr(t *kernel.Task, d *fs.Dirent, dirPath bool, nameAddr, valueAddr usermem.Addr, size uint, flags uint32) error { +// setXattr implements setxattr(2) from the given *fs.Dirent. +func setXattr(t *kernel.Task, d *fs.Dirent, dirPath bool, nameAddr, valueAddr usermem.Addr, size uint64, flags uint32) error { if dirPath && !fs.IsDir(d.Inode.StableAttr) { return syserror.ENOTDIR } @@ -136,7 +142,7 @@ func setxattr(t *kernel.Task, d *fs.Dirent, dirPath bool, nameAddr, valueAddr us return syserror.EOPNOTSUPP } - return d.Inode.Setxattr(name, value) + return d.Inode.SetXattr(t, name, value, flags) } func copyInXattrName(t *kernel.Task, nameAddr usermem.Addr) (string, error) { -- cgit v1.2.3