[PATCH v2 4/4] makedumpfile: print error when reading with unsupported compression

[Philipp Rudo]

Currently makedumpfile only checks if the required compression algorithm
was enabled during build when compressing a dump but not when reading
from one. This can lead to situations where, one version of makedumpfile
creates the dump using a compression algorithm an other version of
makedumpfile doesn't support. When the second version now tries to, e.g.
extract the dmesg from the dump it will fail with an error similar to

	# makedumpfile --dump-dmesg vmcore dmesg.txt
	__vtop4_x86_64: Can't get a valid pgd.
	readmem: Can't convert a virtual address(ffffffff92e18284) to physical address.
	readmem: type_addr: 0, addr:ffffffff92e18284, size:390
	check_release: Can't get the address of system_utsname.

	makedumpfile Failed.

That's because readpage_kdump_compressed{_parallel} does not return
with an error if the page it is trying to read is compressed with an
unsupported compression algorithm. Thus readmem copies random data from
the (uninitialized) cachebuf to its caller and thus causing the error
above.

Fix this by checking if the required compression algorithm is supported
in readpage_kdump_compressed{_parallel} and print a proper error message
if it isn't.

Reported-by: Dave Wysochanski <dwysocha at redhat.com>
Signed-off-by: Philipp Rudo <prudo at redhat.com>
---
 makedumpfile.c | 56 ++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 48 insertions(+), 8 deletions(-)

diff --git a/makedumpfile.c b/makedumpfile.c
index b7ac999..56f3b6c 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -865,9 +865,14 @@ readpage_kdump_compressed(unsigned long long paddr, void *bufptr)
 			ERRMSG("Uncompress failed: %d\n", ret);
 			goto out_error;
 		}
+	} else if ((pd.flags & DUMP_DH_COMPRESSED_LZO)) {
 #ifdef USELZO
-	} else if (info->flag_lzo_support
-		   && (pd.flags & DUMP_DH_COMPRESSED_LZO)) {
+		if (!info->flag_lzo_support) {
+			ERRMSG("lzo compression unsupported\n");
+			out = FALSE;
+			goto out_error;
+		}
+
 		retlen = info->page_size;
 		ret = lzo1x_decompress_safe((unsigned char *)buf, pd.size,
 					    (unsigned char *)bufptr, &retlen,
@@ -876,9 +881,14 @@ readpage_kdump_compressed(unsigned long long paddr, void *bufptr)
 			ERRMSG("Uncompress failed: %d\n", ret);
 			goto out_error;
 		}
+#else
+		ERRMSG("lzo compression unsupported\n");
+		ERRMSG("Try `make USELZO=on` when building.\n");
+		out = FALSE;
+		goto out_error;
 #endif
-#ifdef USESNAPPY
 	} else if ((pd.flags & DUMP_DH_COMPRESSED_SNAPPY)) {
+#ifdef USESNAPPY
 
 		ret = snappy_uncompressed_length(buf, pd.size, (size_t *)&retlen);
 		if (ret != SNAPPY_OK) {
@@ -891,14 +901,24 @@ readpage_kdump_compressed(unsigned long long paddr, void *bufptr)
 			ERRMSG("Uncompress failed: %d\n", ret);
 			goto out_error;
 		}
+#else
+		ERRMSG("snappy compression unsupported\n");
+		ERRMSG("Try `make USESNAPPY=on` when building.\n");
+		out = FALSE;
+		goto out_error;
 #endif
-#ifdef USEZSTD
 	} else if ((pd.flags & DUMP_DH_COMPRESSED_ZSTD)) {
+#ifdef USEZSTD
 		ret = ZSTD_decompress(bufptr, info->page_size, buf, pd.size);
 		if (ZSTD_isError(ret) || (ret != info->page_size)) {
 			ERRMSG("Uncompress failed: %d\n", ret);
 			goto out_error;
 		}
+#else
+		ERRMSG("zstd compression unsupported\n");
+		ERRMSG("Try `make USEZSTD=on` when building.\n");
+		out = FALSE;
+		goto out_error;
 #endif
 	}
 
@@ -964,9 +984,14 @@ readpage_kdump_compressed_parallel(int fd_memory, unsigned long long paddr,
 			ERRMSG("Uncompress failed: %d\n", ret);
 			goto out_error;
 		}
+	} else if ((pd.flags & DUMP_DH_COMPRESSED_LZO)) {
 #ifdef USELZO
-	} else if (info->flag_lzo_support
-		   && (pd.flags & DUMP_DH_COMPRESSED_LZO)) {
+		if (!info->flag_lzo_support) {
+			ERRMSG("lzo compression unsupported\n");
+			out = FALSE;
+			goto out_error;
+		}
+
 		retlen = info->page_size;
 		ret = lzo1x_decompress_safe((unsigned char *)buf, pd.size,
 					    (unsigned char *)bufptr, &retlen,
@@ -975,9 +1000,14 @@ readpage_kdump_compressed_parallel(int fd_memory, unsigned long long paddr,
 			ERRMSG("Uncompress failed: %d\n", ret);
 			goto out_error;
 		}
+#else
+		ERRMSG("lzo compression unsupported\n");
+		ERRMSG("Try `make USELZO=on` when building.\n");
+		out = FALSE;
+		goto out_error;
 #endif
-#ifdef USESNAPPY
 	} else if ((pd.flags & DUMP_DH_COMPRESSED_SNAPPY)) {
+#ifdef USESNAPPY
 
 		ret = snappy_uncompressed_length(buf, pd.size, (size_t *)&retlen);
 		if (ret != SNAPPY_OK) {
@@ -990,14 +1020,24 @@ readpage_kdump_compressed_parallel(int fd_memory, unsigned long long paddr,
 			ERRMSG("Uncompress failed: %d\n", ret);
 			goto out_error;
 		}
+#else
+		ERRMSG("snappy compression unsupported\n");
+		ERRMSG("Try `make USESNAPPY=on` when building.\n");
+		out = FALSE;
+		goto out_error;
 #endif
-#ifdef USEZSTD
 	} else if ((pd.flags & DUMP_DH_COMPRESSED_ZSTD)) {
+#ifdef USEZSTD
 		ret = ZSTD_decompress(bufptr, info->page_size, buf, pd.size);
 		if (ZSTD_isError(ret) || (ret != info->page_size)) {
 			ERRMSG("Uncompress failed: %d\n", ret);
 			goto out_error;
 		}
+#else
+		ERRMSG("zstd compression unsupported\n");
+		ERRMSG("Try `make USEZSTD=on` when building.\n");
+		out = FALSE;
+		goto out_error;
 #endif
 	}
 
-- 
2.35.1