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Diffstat (limited to 'pkg/sentry/usermem/usermem.go')
| -rw-r--r-- | pkg/sentry/usermem/usermem.go | 587 |
1 files changed, 587 insertions, 0 deletions
diff --git a/pkg/sentry/usermem/usermem.go b/pkg/sentry/usermem/usermem.go new file mode 100644 index 000000000..31e4d6ada --- /dev/null +++ b/pkg/sentry/usermem/usermem.go @@ -0,0 +1,587 @@ +// Copyright 2018 The gVisor Authors. +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +// Package usermem governs access to user memory. +package usermem + +import ( + "errors" + "io" + "strconv" + + "gvisor.googlesource.com/gvisor/pkg/binary" + "gvisor.googlesource.com/gvisor/pkg/sentry/context" + "gvisor.googlesource.com/gvisor/pkg/sentry/safemem" + "gvisor.googlesource.com/gvisor/pkg/syserror" +) + +// IO provides access to the contents of a virtual memory space. +// +// FIXME(b/38173783): Implementations of IO cannot expect ctx to contain any +// meaningful data. +type IO interface { + // CopyOut copies len(src) bytes from src to the memory mapped at addr. It + // returns the number of bytes copied. If the number of bytes copied is < + // len(src), it returns a non-nil error explaining why. + // + // Preconditions: The caller must not hold mm.MemoryManager.mappingMu or + // any following locks in the lock order. + // + // Postconditions: CopyOut does not retain src. + CopyOut(ctx context.Context, addr Addr, src []byte, opts IOOpts) (int, error) + + // CopyIn copies len(dst) bytes from the memory mapped at addr to dst. + // It returns the number of bytes copied. If the number of bytes copied is + // < len(dst), it returns a non-nil error explaining why. + // + // Preconditions: The caller must not hold mm.MemoryManager.mappingMu or + // any following locks in the lock order. + // + // Postconditions: CopyIn does not retain dst. + CopyIn(ctx context.Context, addr Addr, dst []byte, opts IOOpts) (int, error) + + // ZeroOut sets toZero bytes to 0, starting at addr. It returns the number + // of bytes zeroed. If the number of bytes zeroed is < toZero, it returns a + // non-nil error explaining why. + // + // Preconditions: The caller must not hold mm.MemoryManager.mappingMu or + // any following locks in the lock order. toZero >= 0. + ZeroOut(ctx context.Context, addr Addr, toZero int64, opts IOOpts) (int64, error) + + // CopyOutFrom copies ars.NumBytes() bytes from src to the memory mapped at + // ars. It returns the number of bytes copied, which may be less than the + // number of bytes read from src if copying fails. CopyOutFrom may return a + // partial copy without an error iff src.ReadToBlocks returns a partial + // read without an error. + // + // CopyOutFrom calls src.ReadToBlocks at most once. + // + // Preconditions: The caller must not hold mm.MemoryManager.mappingMu or + // any following locks in the lock order. src.ReadToBlocks must not block + // on mm.MemoryManager.activeMu or any preceding locks in the lock order. + CopyOutFrom(ctx context.Context, ars AddrRangeSeq, src safemem.Reader, opts IOOpts) (int64, error) + + // CopyInTo copies ars.NumBytes() bytes from the memory mapped at ars to + // dst. It returns the number of bytes copied. CopyInTo may return a + // partial copy without an error iff dst.WriteFromBlocks returns a partial + // write without an error. + // + // CopyInTo calls dst.WriteFromBlocks at most once. + // + // Preconditions: The caller must not hold mm.MemoryManager.mappingMu or + // any following locks in the lock order. dst.WriteFromBlocks must not + // block on mm.MemoryManager.activeMu or any preceding locks in the lock + // order. + CopyInTo(ctx context.Context, ars AddrRangeSeq, dst safemem.Writer, opts IOOpts) (int64, error) + + // TODO(jamieliu): The requirement that CopyOutFrom/CopyInTo call src/dst + // at most once, which is unnecessary in most cases, forces implementations + // to gather safemem.Blocks into a single slice to pass to src/dst. Add + // CopyOutFromIter/CopyInToIter, which relaxes this restriction, to avoid + // this allocation. + + // SwapUint32 atomically sets the uint32 value at addr to new and + // returns the previous value. + // + // Preconditions: The caller must not hold mm.MemoryManager.mappingMu or + // any following locks in the lock order. addr must be aligned to a 4-byte + // boundary. + SwapUint32(ctx context.Context, addr Addr, new uint32, opts IOOpts) (uint32, error) + + // CompareAndSwapUint32 atomically compares the uint32 value at addr to + // old; if they are equal, the value in memory is replaced by new. In + // either case, the previous value stored in memory is returned. + // + // Preconditions: The caller must not hold mm.MemoryManager.mappingMu or + // any following locks in the lock order. addr must be aligned to a 4-byte + // boundary. + CompareAndSwapUint32(ctx context.Context, addr Addr, old, new uint32, opts IOOpts) (uint32, error) + + // LoadUint32 atomically loads the uint32 value at addr and returns it. + // + // Preconditions: The caller must not hold mm.MemoryManager.mappingMu or + // any following locks in the lock order. addr must be aligned to a 4-byte + // boundary. + LoadUint32(ctx context.Context, addr Addr, opts IOOpts) (uint32, error) +} + +// IOOpts contains options applicable to all IO methods. +type IOOpts struct { + // If IgnorePermissions is true, application-defined memory protections set + // by mmap(2) or mprotect(2) will be ignored. (Memory protections required + // by the target of the mapping are never ignored.) + IgnorePermissions bool + + // If AddressSpaceActive is true, the IO implementation may assume that it + // has an active AddressSpace and can therefore use AddressSpace copying + // without performing activation. See mm/io.go for details. + AddressSpaceActive bool +} + +// IOReadWriter is an io.ReadWriter that reads from / writes to addresses +// starting at addr in IO. The preconditions that apply to IO.CopyIn and +// IO.CopyOut also apply to IOReadWriter.Read and IOReadWriter.Write +// respectively. +type IOReadWriter struct { + Ctx context.Context + IO IO + Addr Addr + Opts IOOpts +} + +// Read implements io.Reader.Read. +// +// Note that an address space does not have an "end of file", so Read can only +// return io.EOF if IO.CopyIn returns io.EOF. Attempts to read unmapped or +// unreadable memory, or beyond the end of the address space, should return +// EFAULT. +func (rw *IOReadWriter) Read(dst []byte) (int, error) { + n, err := rw.IO.CopyIn(rw.Ctx, rw.Addr, dst, rw.Opts) + end, ok := rw.Addr.AddLength(uint64(n)) + if ok { + rw.Addr = end + } else { + // Disallow wraparound. + rw.Addr = ^Addr(0) + if err != nil { + err = syserror.EFAULT + } + } + return n, err +} + +// Writer implements io.Writer.Write. +func (rw *IOReadWriter) Write(src []byte) (int, error) { + n, err := rw.IO.CopyOut(rw.Ctx, rw.Addr, src, rw.Opts) + end, ok := rw.Addr.AddLength(uint64(n)) + if ok { + rw.Addr = end + } else { + // Disallow wraparound. + rw.Addr = ^Addr(0) + if err != nil { + err = syserror.EFAULT + } + } + return n, err +} + +// CopyObjectOut copies a fixed-size value or slice of fixed-size values from +// src to the memory mapped at addr in uio. It returns the number of bytes +// copied. +// +// CopyObjectOut must use reflection to encode src; performance-sensitive +// clients should do encoding manually and use uio.CopyOut directly. +// +// Preconditions: As for IO.CopyOut. +func CopyObjectOut(ctx context.Context, uio IO, addr Addr, src interface{}, opts IOOpts) (int, error) { + w := &IOReadWriter{ + Ctx: ctx, + IO: uio, + Addr: addr, + Opts: opts, + } + // Allocate a byte slice the size of the object being marshaled. This + // adds an extra reflection call, but avoids needing to grow the slice + // during encoding, which can result in many heap-allocated slices. + b := make([]byte, 0, binary.Size(src)) + return w.Write(binary.Marshal(b, ByteOrder, src)) +} + +// CopyObjectIn copies a fixed-size value or slice of fixed-size values from +// the memory mapped at addr in uio to dst. It returns the number of bytes +// copied. +// +// CopyObjectIn must use reflection to decode dst; performance-sensitive +// clients should use uio.CopyIn directly and do decoding manually. +// +// Preconditions: As for IO.CopyIn. +func CopyObjectIn(ctx context.Context, uio IO, addr Addr, dst interface{}, opts IOOpts) (int, error) { + r := &IOReadWriter{ + Ctx: ctx, + IO: uio, + Addr: addr, + Opts: opts, + } + buf := make([]byte, binary.Size(dst)) + if _, err := io.ReadFull(r, buf); err != nil { + return 0, err + } + binary.Unmarshal(buf, ByteOrder, dst) + return int(r.Addr - addr), nil +} + +// copyStringIncrement is the maximum number of bytes that are copied from +// virtual memory at a time by CopyStringIn. +const copyStringIncrement = 64 + +// CopyStringIn copies a NUL-terminated string of unknown length from the +// memory mapped at addr in uio and returns it as a string (not including the +// trailing NUL). If the length of the string, including the terminating NUL, +// would exceed maxlen, CopyStringIn returns the string truncated to maxlen and +// ENAMETOOLONG. +// +// Preconditions: As for IO.CopyFromUser. maxlen >= 0. +func CopyStringIn(ctx context.Context, uio IO, addr Addr, maxlen int, opts IOOpts) (string, error) { + buf := make([]byte, maxlen) + var done int + for done < maxlen { + start, ok := addr.AddLength(uint64(done)) + if !ok { + // Last page of kernel memory. The application can't use this + // anyway. + return stringFromImmutableBytes(buf[:done]), syserror.EFAULT + } + // Read up to copyStringIncrement bytes at a time. + readlen := copyStringIncrement + if readlen > maxlen-done { + readlen = maxlen - done + } + end, ok := start.AddLength(uint64(readlen)) + if !ok { + return stringFromImmutableBytes(buf[:done]), syserror.EFAULT + } + // Shorten the read to avoid crossing page boundaries, since faulting + // in a page unnecessarily is expensive. This also ensures that partial + // copies up to the end of application-mappable memory succeed. + if start.RoundDown() != end.RoundDown() { + end = end.RoundDown() + } + n, err := uio.CopyIn(ctx, start, buf[done:done+int(end-start)], opts) + // Look for the terminating zero byte, which may have occurred before + // hitting err. + for i, c := range buf[done : done+n] { + if c == 0 { + return stringFromImmutableBytes(buf[:done+i]), nil + } + } + done += n + if err != nil { + return stringFromImmutableBytes(buf[:done]), err + } + } + return stringFromImmutableBytes(buf), syserror.ENAMETOOLONG +} + +// CopyOutVec copies bytes from src to the memory mapped at ars in uio. The +// maximum number of bytes copied is ars.NumBytes() or len(src), whichever is +// less. CopyOutVec returns the number of bytes copied; if this is less than +// the maximum, it returns a non-nil error explaining why. +// +// Preconditions: As for IO.CopyOut. +func CopyOutVec(ctx context.Context, uio IO, ars AddrRangeSeq, src []byte, opts IOOpts) (int, error) { + var done int + for !ars.IsEmpty() && done < len(src) { + ar := ars.Head() + cplen := len(src) - done + if Addr(cplen) >= ar.Length() { + cplen = int(ar.Length()) + } + n, err := uio.CopyOut(ctx, ar.Start, src[done:done+cplen], opts) + done += n + if err != nil { + return done, err + } + ars = ars.DropFirst(n) + } + return done, nil +} + +// CopyInVec copies bytes from the memory mapped at ars in uio to dst. The +// maximum number of bytes copied is ars.NumBytes() or len(dst), whichever is +// less. CopyInVec returns the number of bytes copied; if this is less than the +// maximum, it returns a non-nil error explaining why. +// +// Preconditions: As for IO.CopyIn. +func CopyInVec(ctx context.Context, uio IO, ars AddrRangeSeq, dst []byte, opts IOOpts) (int, error) { + var done int + for !ars.IsEmpty() && done < len(dst) { + ar := ars.Head() + cplen := len(dst) - done + if Addr(cplen) >= ar.Length() { + cplen = int(ar.Length()) + } + n, err := uio.CopyIn(ctx, ar.Start, dst[done:done+cplen], opts) + done += n + if err != nil { + return done, err + } + ars = ars.DropFirst(n) + } + return done, nil +} + +// ZeroOutVec writes zeroes to the memory mapped at ars in uio. The maximum +// number of bytes written is ars.NumBytes() or toZero, whichever is less. +// ZeroOutVec returns the number of bytes written; if this is less than the +// maximum, it returns a non-nil error explaining why. +// +// Preconditions: As for IO.ZeroOut. +func ZeroOutVec(ctx context.Context, uio IO, ars AddrRangeSeq, toZero int64, opts IOOpts) (int64, error) { + var done int64 + for !ars.IsEmpty() && done < toZero { + ar := ars.Head() + cplen := toZero - done + if Addr(cplen) >= ar.Length() { + cplen = int64(ar.Length()) + } + n, err := uio.ZeroOut(ctx, ar.Start, cplen, opts) + done += n + if err != nil { + return done, err + } + ars = ars.DropFirst64(n) + } + return done, nil +} + +func isASCIIWhitespace(b byte) bool { + // Compare Linux include/linux/ctype.h, lib/ctype.c. + // 9 => horizontal tab '\t' + // 10 => line feed '\n' + // 11 => vertical tab '\v' + // 12 => form feed '\c' + // 13 => carriage return '\r' + return b == ' ' || (b >= 9 && b <= 13) +} + +// CopyInt32StringsInVec copies up to len(dsts) whitespace-separated decimal +// strings from the memory mapped at ars in uio and converts them to int32 +// values in dsts. It returns the number of bytes read. +// +// CopyInt32StringsInVec shares the following properties with Linux's +// kernel/sysctl.c:proc_dointvec(write=1): +// +// - If any read value overflows the range of int32, or any invalid characters +// are encountered during the read, CopyInt32StringsInVec returns EINVAL. +// +// - If, upon reaching the end of ars, fewer than len(dsts) values have been +// read, CopyInt32StringsInVec returns no error if at least 1 value was read +// and EINVAL otherwise. +// +// - Trailing whitespace after the last successfully read value is counted in +// the number of bytes read. +// +// Unlike proc_dointvec(): +// +// - CopyInt32StringsInVec does not implicitly limit ars.NumBytes() to +// PageSize-1; callers that require this must do so explicitly. +// +// - CopyInt32StringsInVec returns EINVAL if ars.NumBytes() == 0. +// +// Preconditions: As for CopyInVec. +func CopyInt32StringsInVec(ctx context.Context, uio IO, ars AddrRangeSeq, dsts []int32, opts IOOpts) (int64, error) { + if len(dsts) == 0 { + return 0, nil + } + + buf := make([]byte, ars.NumBytes()) + n, cperr := CopyInVec(ctx, uio, ars, buf, opts) + buf = buf[:n] + + var i, j int + for ; j < len(dsts); j++ { + // Skip leading whitespace. + for i < len(buf) && isASCIIWhitespace(buf[i]) { + i++ + } + if i == len(buf) { + break + } + + // Find the end of the value to be parsed (next whitespace or end of string). + nextI := i + 1 + for nextI < len(buf) && !isASCIIWhitespace(buf[nextI]) { + nextI++ + } + + // Parse a single value. + val, err := strconv.ParseInt(string(buf[i:nextI]), 10, 32) + if err != nil { + return int64(i), syserror.EINVAL + } + dsts[j] = int32(val) + + i = nextI + } + + // Skip trailing whitespace. + for i < len(buf) && isASCIIWhitespace(buf[i]) { + i++ + } + + if cperr != nil { + return int64(i), cperr + } + if j == 0 { + return int64(i), syserror.EINVAL + } + return int64(i), nil +} + +// CopyInt32StringInVec is equivalent to CopyInt32StringsInVec, but copies at +// most one int32. +func CopyInt32StringInVec(ctx context.Context, uio IO, ars AddrRangeSeq, dst *int32, opts IOOpts) (int64, error) { + dsts := [1]int32{*dst} + n, err := CopyInt32StringsInVec(ctx, uio, ars, dsts[:], opts) + *dst = dsts[0] + return n, err +} + +// IOSequence holds arguments to IO methods. +type IOSequence struct { + IO IO + Addrs AddrRangeSeq + Opts IOOpts +} + +// NumBytes returns s.Addrs.NumBytes(). +// +// Note that NumBytes() may return 0 even if !s.Addrs.IsEmpty(), since +// s.Addrs may contain a non-zero number of zero-length AddrRanges. +// Many clients of +// IOSequence currently do something like: +// +// if ioseq.NumBytes() == 0 { +// return 0, nil +// } +// if f.availableBytes == 0 { +// return 0, syserror.ErrWouldBlock +// } +// return ioseq.CopyOutFrom(..., reader) +// +// In such cases, using s.Addrs.IsEmpty() will cause them to have the wrong +// behavior for zero-length I/O. However, using s.NumBytes() == 0 instead means +// that we will return success for zero-length I/O in cases where Linux would +// return EFAULT due to a failed access_ok() check, so in the long term we +// should move checks for ErrWouldBlock etc. into the body of +// reader.ReadToBlocks and use s.Addrs.IsEmpty() instead. +func (s IOSequence) NumBytes() int64 { + return s.Addrs.NumBytes() +} + +// DropFirst returns a copy of s with s.Addrs.DropFirst(n). +// +// Preconditions: As for AddrRangeSeq.DropFirst. +func (s IOSequence) DropFirst(n int) IOSequence { + return IOSequence{s.IO, s.Addrs.DropFirst(n), s.Opts} +} + +// DropFirst64 returns a copy of s with s.Addrs.DropFirst64(n). +// +// Preconditions: As for AddrRangeSeq.DropFirst64. +func (s IOSequence) DropFirst64(n int64) IOSequence { + return IOSequence{s.IO, s.Addrs.DropFirst64(n), s.Opts} +} + +// TakeFirst returns a copy of s with s.Addrs.TakeFirst(n). +// +// Preconditions: As for AddrRangeSeq.TakeFirst. +func (s IOSequence) TakeFirst(n int) IOSequence { + return IOSequence{s.IO, s.Addrs.TakeFirst(n), s.Opts} +} + +// TakeFirst64 returns a copy of s with s.Addrs.TakeFirst64(n). +// +// Preconditions: As for AddrRangeSeq.TakeFirst64. +func (s IOSequence) TakeFirst64(n int64) IOSequence { + return IOSequence{s.IO, s.Addrs.TakeFirst64(n), s.Opts} +} + +// CopyOut invokes CopyOutVec over s.Addrs. +// +// As with CopyOutVec, if s.NumBytes() < len(src), the copy will be truncated +// to s.NumBytes(), and a nil error will be returned. +// +// Preconditions: As for CopyOutVec. +func (s IOSequence) CopyOut(ctx context.Context, src []byte) (int, error) { + return CopyOutVec(ctx, s.IO, s.Addrs, src, s.Opts) +} + +// CopyIn invokes CopyInVec over s.Addrs. +// +// As with CopyInVec, if s.NumBytes() < len(dst), the copy will be truncated to +// s.NumBytes(), and a nil error will be returned. +// +// Preconditions: As for CopyInVec. +func (s IOSequence) CopyIn(ctx context.Context, dst []byte) (int, error) { + return CopyInVec(ctx, s.IO, s.Addrs, dst, s.Opts) +} + +// ZeroOut invokes ZeroOutVec over s.Addrs. +// +// As with ZeroOutVec, if s.NumBytes() < toZero, the write will be truncated +// to s.NumBytes(), and a nil error will be returned. +// +// Preconditions: As for ZeroOutVec. +func (s IOSequence) ZeroOut(ctx context.Context, toZero int64) (int64, error) { + return ZeroOutVec(ctx, s.IO, s.Addrs, toZero, s.Opts) +} + +// CopyOutFrom invokes s.CopyOutFrom over s.Addrs. +// +// Preconditions: As for IO.CopyOutFrom. +func (s IOSequence) CopyOutFrom(ctx context.Context, src safemem.Reader) (int64, error) { + return s.IO.CopyOutFrom(ctx, s.Addrs, src, s.Opts) +} + +// CopyInTo invokes s.CopyInTo over s.Addrs. +// +// Preconditions: As for IO.CopyInTo. +func (s IOSequence) CopyInTo(ctx context.Context, dst safemem.Writer) (int64, error) { + return s.IO.CopyInTo(ctx, s.Addrs, dst, s.Opts) +} + +// Reader returns an io.Reader that reads from s. Reads beyond the end of s +// return io.EOF. The preconditions that apply to s.CopyIn also apply to the +// returned io.Reader.Read. +func (s IOSequence) Reader(ctx context.Context) io.Reader { + return &ioSequenceReadWriter{ctx, s} +} + +// Writer returns an io.Writer that writes to s. Writes beyond the end of s +// return ErrEndOfIOSequence. The preconditions that apply to s.CopyOut also +// apply to the returned io.Writer.Write. +func (s IOSequence) Writer(ctx context.Context) io.Writer { + return &ioSequenceReadWriter{ctx, s} +} + +// ErrEndOfIOSequence is returned by IOSequence.Writer().Write() when +// attempting to write beyond the end of the IOSequence. +var ErrEndOfIOSequence = errors.New("write beyond end of IOSequence") + +type ioSequenceReadWriter struct { + ctx context.Context + s IOSequence +} + +// Read implements io.Reader.Read. +func (rw *ioSequenceReadWriter) Read(dst []byte) (int, error) { + n, err := rw.s.CopyIn(rw.ctx, dst) + rw.s = rw.s.DropFirst(n) + if err == nil && rw.s.NumBytes() == 0 { + err = io.EOF + } + return n, err +} + +// Write implements io.Writer.Write. +func (rw *ioSequenceReadWriter) Write(src []byte) (int, error) { + n, err := rw.s.CopyOut(rw.ctx, src) + rw.s = rw.s.DropFirst(n) + if err == nil && n < len(src) { + err = ErrEndOfIOSequence + } + return n, err +} |