fix: broken pnm files with invalid resolution

src/libutil/strutil.cpp

@@ -1669,8 +1669,9 @@ Strutil::stoi(string_view str, size_t* pos, int base)
         }
         if (c >= base)
             break;
-        acc       = acc * base + c;
         anydigits = true;
+        if (OIIO_LIKELY(!overflow))
+            acc = acc * base + c;
         if (OIIO_UNLIKELY(acc > maxval))
             overflow = true;
     }

src/libutil/strutil_test.cpp

@@ -891,6 +891,7 @@ test_numeric_conversion()
     OIIO_CHECK_EQUAL(Strutil::stoi("-12345678901234567890"),
                      std::numeric_limits<int>::min());
     OIIO_CHECK_EQUAL(Strutil::stoi("0x100", nullptr, 16), 256);  // hex
+    OIIO_CHECK_EQUAL(Strutil::stoi("25555555555555555551"), 2147483647);
 
     OIIO_CHECK_EQUAL(Strutil::stoui("hi"), 0);
     OIIO_CHECK_EQUAL(Strutil::stoui("  "), 0);

src/pnm.imageio/pnminput.cpp

@@ -377,6 +377,9 @@ PNMInput::open(const std::string& name, ImageSpec& newspec)
     if (!read_file_header())
         return false;
 
+    if (!check_open(m_spec))  // check for apparently invalid values
+        return false;
+
     newspec = m_spec;
     return true;
 }

testsuite/pnm/ref/out.txt

@@ -69,3 +69,6 @@ Reading ../oiio-images/pnm/test-3.pfm
     oiio:ColorSpace: "Rec709"
     pnm:bigendian: 1
     pnm:binary: 1
+oiiotool ERROR: read : "src/bad-4553.pgm": pnm image resolution may not exceed 65535x65535, but the file appears to be 2147483647x255. Possible corrupt input?
+Full command line was:
+> oiiotool --info -v -a --hash --oiioattrib try_all_readers 0 --printstats src/bad-4553.pgm

testsuite/pnm/run.py

@@ -4,6 +4,8 @@
 # SPDX-License-Identifier: Apache-2.0
 # https://github.com/AcademySoftwareFoundation/OpenImageIO
 
+redirect = ' >> out.txt 2>&1 '
+
 imagedir = OIIO_TESTSUITE_IMAGEDIR + "/pnm"
 
 for f in [ "bw-ascii.pbm", "bw-binary.pbm",
@@ -16,3 +18,8 @@
 for f in files:
     command += info_command (imagedir + "/" + f,
                              safematch=True, hash=True)
+
+# Damaged files
+files = [ "src/bad-4553.pgm" ]
+for f in files:
+    command += info_command (f, extraargs="--oiioattrib try_all_readers 0 --printstats", failureok=True)

testsuite/pnm/src/bad-4553.pgm

@@ -0,0 +1,4 @@
+P1
+25555555555555555551
+255
+�