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48 lines
2.0 KiB
48 lines
2.0 KiB
2 weeks ago
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From FEDORA_PATCHES Mon Sep 17 00:00:00 2001
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From: Keith Seitz <keiths@redhat.com>
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Date: Tue, 5 Dec 2023 08:47:16 -0800
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Subject: gdb-find_and_open_source-empty-string-ub-3of4.patch
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;; Backport "Fix undefined behaviour dereferencing empty string"
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;; (Magne Hov, RHEL-17631)
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When a source file's dirname is solely made up of directory separators
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we end up trying to dereference the last character of an empty string
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with std::string::back, which results in undefined behaviour. A typical
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use case where this can happen is when the root directory "/" is used as
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a compilation directory.
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With libstdc++.so.6.0.28 we get no out-of-bounds checks and the byte
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preceding the storage of the empty string is returned. The character
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value of this byte depends on heap implementation and usage, but when
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this byte happens to hold the value of the directory separator character
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we go on to call std::string::pop_back on the empty string which results
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in an out_of_range exception which terminates GDB.
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Fix this by using path_join. prepare_path_for_appending ensures that the
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filename component is relative.
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The testsuite has been run before and after the change and no
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regressions were found.
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diff --git a/gdb/source.c b/gdb/source.c
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--- a/gdb/source.c
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+++ b/gdb/source.c
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@@ -1111,15 +1111,7 @@ find_and_open_source (const char *filename,
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helpful if part of the compilation directory was removed,
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e.g. using gcc's -fdebug-prefix-map, and we have added the missing
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prefix to source_path. */
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- std::string cdir_filename (dirname);
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-
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- /* Remove any trailing directory separators. */
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- while (IS_DIR_SEPARATOR (cdir_filename.back ()))
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- cdir_filename.pop_back ();
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-
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- /* Add our own directory separator. */
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- cdir_filename.append (SLASH_STRING);
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- cdir_filename.append (filename_start);
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+ std::string cdir_filename = path_join (dirname, filename_start);
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result = openp (path, OPF_SEARCH_IN_PATH | OPF_RETURN_REALPATH,
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cdir_filename.c_str (), OPEN_MODE, fullname);
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