X-Git-Url: http://mj.ucw.cz/gitweb/?a=blobdiff_plain;f=lib%2Flizard-safe.c;h=88e9aebd4fc8070a1a97e239d487b8fd8a1b6963;hb=b1fd07e17d8b9041fd026385e51f273adb2bee5a;hp=fb45f8bf17f8a6d83b694485f8ed10dc80f009fd;hpb=159f3fd2f4b044788fc71208855ed1a846b20949;p=libucw.git

diff --git a/lib/lizard-safe.c b/lib/lizard-safe.c
index fb45f8bf..88e9aebd 100644
--- a/lib/lizard-safe.c
+++ b/lib/lizard-safe.c
@@ -18,64 +18,88 @@
 #include <setjmp.h>
 #include <errno.h>
 
+struct lizard_buffer {
+  uns len;
+  void *ptr;
+  struct sigaction old_sigsegv_handler;
+};
+
 struct lizard_buffer *
-lizard_alloc(uns max_len)
+lizard_alloc(void)
 {
-  static byte *zero = "/dev/zero";
-  int fd = open(zero, O_RDWR);
-  if (fd < 0)
-    die("open(%s): %m", zero);
   struct lizard_buffer *buf = xmalloc(sizeof(struct lizard_buffer));
-  buf->len = ALIGN(max_len + PAGE_SIZE, PAGE_SIZE);
-  buf->ptr = mmap(NULL, buf->len, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
-  if (buf->ptr == MAP_FAILED)
-    die("mmap(%s): %m", zero);
+  buf->len = 0;
+  buf->ptr = NULL;
+  handle_signal(SIGSEGV, &buf->old_sigsegv_handler);
   return buf;
 }
 
 void
 lizard_free(struct lizard_buffer *buf)
 {
-  munmap(buf->ptr, buf->len);
+  if (buf->ptr)
+    munmap(buf->ptr, buf->len + PAGE_SIZE);
+  unhandle_signal(SIGSEGV, &buf->old_sigsegv_handler);
   xfree(buf);
 }
 
-static jmp_buf safe_decompress_jump;
 static void
-sigsegv_handler(int UNUSED whatsit)
+lizard_realloc(struct lizard_buffer *buf, uns max_len)
+  /* max_len needs to be aligned to PAGE_SIZE */
+{
+  if (max_len <= buf->len)
+    return;
+  if (max_len < 2*buf->len)				// to ensure logarithmic cost
+    max_len = 2*buf->len;
+
+  if (buf->ptr)
+    munmap(buf->ptr, buf->len + PAGE_SIZE);
+  buf->len = max_len;
+  buf->ptr = mmap(NULL, buf->len + PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  if (buf->ptr == MAP_FAILED)
+    die("mmap(anonymous): %m");
+  if (mprotect(buf->ptr + buf->len, PAGE_SIZE, PROT_NONE) < 0)
+    die("mprotect: %m");
+}
+
+static jmp_buf safe_decompress_jump;
+static int
+sigsegv_handler(int signal UNUSED)
 {
   log(L_ERROR, "SIGSEGV caught in lizard_decompress()");
   longjmp(safe_decompress_jump, 1);
+  return 1;
 }
 
-int
+byte *
 lizard_decompress_safe(byte *in, struct lizard_buffer *buf, uns expected_length)
-  /* Decompresses into buf->ptr and returns the length of the uncompressed
-   * file.  If an error has occured, -1 is returned and errno is set.  SIGSEGV
-   * is caught in the case of buffer-overflow.  The function is not re-entrant
-   * because of a static longjmp handler.  */
+  /* Decompresses in into buf, sets *ptr to the data, and returns the
+   * uncompressed length.  If an error has occured, -1 is returned and errno is
+   * set.  The buffer buf is automatically reallocated.  SIGSEGV is caught in
+   * case of buffer-overflow.  The function is not re-entrant because of a
+   * static longjmp handler.  */
 {
-  uns lock_offset = ALIGN(expected_length, PAGE_SIZE);
-  if (lock_offset + PAGE_SIZE > buf->len)
-  {
-    errno = EFBIG;
-    return -1;
-  }
-  mprotect(buf->ptr + lock_offset, PAGE_SIZE, PROT_NONE);
-  volatile sighandler_t old_handler = signal(SIGSEGV, sigsegv_handler);
-  int len, err;
+  uns lock_offset = ALIGN(expected_length + 3, PAGE_SIZE);	// +3 due to the unaligned access
+  if (lock_offset > buf->len)
+    lizard_realloc(buf, lock_offset);
+  volatile sh_sighandler_t old_handler = signal_handler[SIGSEGV];
+  signal_handler[SIGSEGV] = sigsegv_handler;
+  byte *ptr;
   if (!setjmp(safe_decompress_jump))
   {
-    len = lizard_decompress(in, buf->ptr);
-    err = errno;
+    ptr = buf->ptr + buf->len - lock_offset;
+    int len = lizard_decompress(in, ptr);
+    if (len != (int) expected_length)
+    {
+      ptr = NULL;
+      errno = EINVAL;
+    }
   }
   else
   {
-    len = -1;
-    err = EFAULT;
+    ptr = NULL;
+    errno = EFAULT;
   }
-  signal(SIGSEGV, old_handler);
-  mprotect(buf->ptr + lock_offset, PAGE_SIZE, PROT_READ | PROT_WRITE);
-  errno = err;
-  return len;
+  signal_handler[SIGSEGV] = old_handler;
+  return ptr;
 }