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perf tools: Fix uninitialized pathname on uncompressed fallback in filename__decompress()

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filename__decompress() has an early return path for files that are not
actually compressed.  This path returns the fd from open() directly but
never writes to the pathname output parameter, leaving the caller with
an uninitialized buffer despite a successful return.

Callers like dso__decompress_kmodule_path() pass pathname to
decompress_kmodule() which uses it to set the decompressed file path.
If pathname is uninitialized, subsequent operations on the path produce
undefined behavior.

Fix by setting pathname to an empty string on the uncompressed path.
Callers already check for an empty pathname to distinguish temporary
decompressed files (which need unlink) from the original file.

Reported-by: sashiko-bot <sashiko-bot@kernel.org>
Fixes: 7ac22b088a ("perf tools: Add filename__decompress function")
Cc: Jiri Olsa <jolsa@kernel.org>
Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo
2026-06-07 22:43:09 -03:00
parent 1b4e9fbdea
commit 51cdb188ed
4 changed files with 23 additions and 9 deletions
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7
tools/perf/tests/code-reading.c
View File

@@ -471,8 +471,11 @@ static int read_object_code(u64 addr, size_t len, u8 cpumode,
goto out;
}
decomp = true;
objdump_name = decomp_name;
/* empty pathname means file wasn't actually compressed */
if (decomp_name[0] != '\0') {
decomp = true;
objdump_name = decomp_name;
}
}
/* Read the object code using objdump */

7
tools/perf/util/disasm.c
View File

@@ -1577,8 +1577,11 @@ int symbol__disassemble(struct symbol *sym, struct annotate_args *args)
if (dso__decompress_kmodule_path(dso, symfs_filename, tmp, sizeof(tmp)) < 0)
return -1;
decomp = true;
strcpy(symfs_filename, tmp);
/* empty pathname means file wasn't actually compressed */
if (tmp[0] != '\0') {
decomp = true;
strcpy(symfs_filename, tmp);
}
}
/*

12
tools/perf/util/dso.c
View File

@@ -343,8 +343,11 @@ int filename__decompress(const char *name, char *pathname,
* To keep this transparent, we detect this and return the file
* descriptor to the uncompressed file.
*/
if (!compressions[comp].is_compressed(name))
if (!compressions[comp].is_compressed(name)) {
if (pathname && len > 0)
pathname[0] = '\0';
return open(name, O_RDONLY | O_CLOEXEC);
}
fd = mkostemp(tmpbuf, O_CLOEXEC);
if (fd < 0) {
@@ -598,8 +601,11 @@ static char *dso__get_filename(struct dso *dso, const char *root_dir,
goto out;
}
*decomp = true;
strcpy(name, newpath);
/* empty pathname means file wasn't actually compressed */
if (newpath[0] != '\0') {
*decomp = true;
strcpy(name, newpath);
}
}
return name;

6
tools/perf/util/symbol-elf.c
View File

@@ -920,12 +920,14 @@ int filename__read_build_id(const char *filename, struct build_id *bid)
return -1;
}
close(fd);
filename = path;
/* non-empty path means a temp file was created */
if (path[0] != '\0')
filename = path;
}
err = read_build_id(filename, bid);
if (m.comp)
if (m.comp && filename == path)
unlink(filename);
return err;
}