Remove the backdoor found in 5.6.0 and 5.6.1 (CVE-2024-3094).

While the backdoor was inactive (and thus harmless) without inserting
a small trigger code into the build system when the source package was
created, it's good to remove this anyway:

  - The executable payloads were embedded as binary blobs in
    the test files. This was a blatant violation of the
    Debian Free Software Guidelines.

  - On machines that see lots bots poking at the SSH port, the backdoor
    noticeably increased CPU load, resulting in degraded user experience
    and thus overwhelmingly negative user feedback.

  - The maintainer who added the backdoor has disappeared.

  - Backdoors are bad for security.

This reverts the following without making any other changes:

6e636819 Tests: Update two test files.
a3a29bbd Tests: Test --single-stream can decompress bad-3-corrupt_lzma2.xz.
0b4ccc91 Tests: Update RISC-V test files.
8c9b8b20 liblzma: Fix typos in crc32_fast.c and crc64_fast.c.
82ecc538 liblzma: Fix false Valgrind error report with GCC.
cf44e4b7 Tests: Add a few test files.
3060e107 Tests: Use smaller dictionary size in RISC-V test files.
e2870db5 Tests: Add two RISC-V Filter test files.

The RISC-V test files also have real content that tests the filter
but the real content would fit into much smaller files. A generator
program would need to be available as well.

Thanks to Andres Freund for finding and reporting it and making
it public quickly so others could act without a delay.
See: https://www.openwall.com/lists/oss-security/2024/03/29/4

3 files changed, 8 insertions, 28 deletions

diff --git a/src/liblzma/check/crc32_fast.c b/src/liblzma/check/crc32_fast.c
index bfa295a0..079051f1 100644
--- a/src/liblzma/check/crc32_fast.c
+++ b/src/liblzma/check/crc32_fast.c
@@ -135,8 +135,11 @@ typedef uint32_t (*crc32_func_type)(
 // This resolver is shared between all three dispatch methods. It serves as
 // the ifunc resolver if ifunc is supported, otherwise it is called as a
 // regular function by the constructor or first call resolution methods.
-// The function attributes are needed for safe IFUNC resolver usage with GCC.
-lzma_resolver_attributes
+// The __no_profile_instrument_function__ attribute support is checked when
+// determining if ifunc can be used, so it is safe to use here.
+#ifdef CRC_USE_IFUNC
+__attribute__((__no_profile_instrument_function__))
+#endif
 static crc32_func_type
 crc32_resolve(void)
 {
diff --git a/src/liblzma/check/crc64_fast.c b/src/liblzma/check/crc64_fast.c
index 52cddb2c..5728b45e 100644
--- a/src/liblzma/check/crc64_fast.c
+++ b/src/liblzma/check/crc64_fast.c
@@ -98,7 +98,9 @@ typedef uint64_t (*crc64_func_type)(
 #	pragma GCC diagnostic ignored "-Wunused-function"
 #endif
 
-lzma_resolver_attributes
+#ifdef CRC_USE_IFUNC
+__attribute__((__no_profile_instrument_function__))
+#endif
 static crc64_func_type
 crc64_resolve(void)
 {
diff --git a/src/liblzma/check/crc_common.h b/src/liblzma/check/crc_common.h
index 5a86556f..856665db 100644
--- a/src/liblzma/check/crc_common.h
+++ b/src/liblzma/check/crc_common.h
@@ -128,31 +128,6 @@
 #	endif
 #endif
 
-#ifdef CRC_USE_IFUNC
-// Two function attributes are needed to make IFUNC safe with GCC.
-//
-// no-omit-frame-pointer prevents false Valgrind issues when combined with
-// a few other compiler flags. The optimize attribute is supported on
-// GCC >= 4.4 and is not supported with Clang.
-#	if TUKLIB_GNUC_REQ(4,4) && !defined(__clang__)
-#		define no_omit_frame_pointer \
-			__attribute__((optimize("no-omit-frame-pointer")))
-#	else
-#		define no_omit_frame_pointer
-#	endif
-
-// The __no_profile_instrument_function__ attribute support is checked when
-// determining if ifunc can be used, so it is safe to use unconditionally.
-// This attribute is needed because GCC can add profiling to the IFUNC
-// resolver, which calls functions that have not yet been relocated leading
-// to a crash on liblzma start up.
-#	define lzma_resolver_attributes \
-		__attribute__((__no_profile_instrument_function__)) \
-		no_omit_frame_pointer
-#else
-#	define lzma_resolver_attributes
-#endif
-
 // For CRC32 use the generic slice-by-eight implementation if no optimized
 // version is available.
 #if !defined(CRC32_ARCH_OPTIMIZED) && !defined(CRC32_GENERIC)