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We have to copy the dentry->d_name before calling closedir(). If not, the string points to nothing and the test fails (It does not fail all the time, but only by chance). Confirmed using valgrind. Selected output from running the unit test under valgrind: $ valgrind --track-origins=yes ./test_blockSpecial ==25110== Memcheck, a memory error detector ... ==25110== Command: ./test_BlockSpecial ==25110== Running main() from src/gtest_main.cc [==========] Running 26 tests from 1 test case. [----------] Global test environment set-up. [----------] 26 tests from BlockSpecialTest ... [ RUN ] BlockSpecialTest.NamedBlockSpecialObjectBySymlinkMatches ==25110== Invalid read of size 1 ==25110== at 0x4C2C9B2: strlen (vg_replace_strmem.c:458) ==25110== by 0x40E7C4: length (char_traits.h:259) ==25110== by 0x40E7C4: append (basic_string.h:1009) ==25110== by 0x40E7C4: operator+<char, std::char_traits<char>, std::allocator<char> > (basic_string.h:2468) ==25110== by 0x40E7C4: get_link_name (test_BlockSpecial.cc:156) ==25110== by 0x40E7C4: GParted::BlockSpecialTest_NamedBlockSpecialObjectBySymlinkMatches_Test::TestBody() (test_BlockSpecial.cc:247) ... =25110== Address 0x1231ea93 is 115 bytes inside a block of size 32,816 free'd ==25110== at 0x4C2ACBD: free (vg_replace_malloc.c:530) ==25110== by 0x9F773AC: closedir (in /usr/lib64/libc-2.17.so) ==25110== by 0x40E7AC: get_link_name (test_BlockSpecial.cc:153) ==25110== by 0x40E7AC: GParted::BlockSpecialTest_NamedBlockSpecialObjectBySymlinkMatches_Test::TestBody() (test_BlockSpecial.cc:247) ... ==25110== Block was alloc'd at ==25110== at 0x4C29BC3: malloc (vg_replace_malloc.c:299) ==25110== by 0x9F77280: __alloc_dir (in /usr/lib64/libc-2.17.so) ==25110== by 0x40E746: get_link_name (test_BlockSpecial.cc:134) ==25110== by 0x40E746: GParted::BlockSpecialTest_NamedBlockSpecialObjectBySymlinkMatches_Test::TestBody() (test_BlockSpecial.cc:247) ... ==25110== Invalid read of size 1 ==25110== at 0x4C2E220: memcpy@@GLIBC_2.14 (vg_replace_strmem.c:1022) ==25110== by 0x953A997: std::string::append(char const*, unsigned long) (in /usr/lib64/libstdc++.so.6.0.19) ==25110== by 0x40E7D2: append (basic_string.h:1009) ==25110== by 0x40E7D2: operator+<char, std::char_traits<char>, std::allocator<char> > (basic_string.h:2468) ==25110== by 0x40E7D2: get_link_name (test_BlockSpecial.cc:156) ==25110== by 0x40E7D2: GParted::BlockSpecialTest_NamedBlockSpecialObjectBySymlinkMatches_Test::TestBody() (test_BlockSpecial.cc:247) ... ==25110== Address 0x1231ea93 is 115 bytes inside a block of size 32,816 free'd ==25110== at 0x4C2ACBD: free (vg_replace_malloc.c:530) ==25110== by 0x9F773AC: closedir (in /usr/lib64/libc-2.17.so) ==25110== by 0x40E7AC: get_link_name (test_BlockSpecial.cc:153) ==25110== by 0x40E7AC: GParted::BlockSpecialTest_NamedBlockSpecialObjectBySymlinkMatches_Test::TestBody() (test_BlockSpecial.cc:247) ... ==25110== Block was alloc'd at ==25110== at 0x4C29BC3: malloc (vg_replace_malloc.c:299) ==25110== by 0x9F77280: __alloc_dir (in /usr/lib64/libc-2.17.so) ==25110== by 0x40E746: get_link_name (test_BlockSpecial.cc:134) ==25110== by 0x40E746: GParted::BlockSpecialTest_NamedBlockSpecialObjectBySymlinkMatches_Test::TestBody() (test_BlockSpecial.cc:247) ... [ OK ] BlockSpecialTest.NamedBlockSpecialObjectBySymlinkMatches (50 ms) Selected lines from test_BlockSpecial.cc: 132 static std::string get_link_name() 133 { 134 DIR * dir = opendir( "/dev/disk/by-id" ); ... 141 bool found = false; 142 struct dirent * dentry; 143 // Silence GCC [-Wparentheses] warning with double parentheses 144 while ( ( dentry = readdir( dir ) ) ) 145 { 146 if ( strcmp( dentry->d_name, "." ) != 0 && 147 strcmp( dentry->d_name, ". " ) != 0 ) 148 { 149 found = true; 150 break; 151 } 152 } 153 closedir( dir ); 154 155 if ( found ) 156 return std::string( "/dev/disk/by-id/" ) + dentry->d_name; So the memory referred to by dentry was allocated on line 134, freed on 153 and accessed after freed on 156. Closes !41 - Fix test (dentry->d_name is invalidated by closedir...)cdba5cee
