Hello, gently ping. I rephrased the commit message (patch attached).
Pavel
On Thursday, March 30, 2017 2:05:07 PM CEST Pavel Raiskup wrote:
> Heuristic for guessing the archive/compression format works with
> archive magic and tar_checksum() which depends on the first block
> (BLOCKSIZE) of archive data in pre-fetched buffer.
>
> Very small files though (compressed size is smaller than
> BLOCKSIZE) don't initialize a whole data block in buffer, so the
> heuristic calculated with uninitialized data previously. In rare
> situations compressed archives were marked as non-compressed,
> which in turn caused extraction failure.
>
> * src/buffer.c (check_compressed_archive): Don't assume archives
> smaller than BLOCKSIZE could be non-compressed, as tar header has
> always has at least one block.
> ---
> src/buffer.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/src/buffer.c b/src/buffer.c
> index fb34834..f064d2a 100644
> --- a/src/buffer.c
> +++ b/src/buffer.c
> @@ -391,10 +391,12 @@ check_compressed_archive (bool *pshort)
> /* Restore global values */
> read_full_records = sfr;
>
> - if ((strcmp (record_start->header.magic, TMAGIC) == 0 ||
> - strcmp (record_start->buffer + offsetof (struct posix_header, magic),
> - OLDGNU_MAGIC) == 0) &&
> - tar_checksum (record_start, true) == HEADER_SUCCESS)
> + if (record_start != record_end /* no files smaller than BLOCKSIZE */
> + && (strcmp (record_start->header.magic, TMAGIC) == 0
> + || strcmp (record_start->buffer + offsetof (struct posix_header,
> + magic),
> + OLDGNU_MAGIC) == 0)
> + && tar_checksum (record_start, true) == HEADER_SUCCESS)
> /* Probably a valid header */
> return ct_tar;
>
>
>From 3fe273c4ee7b0c29be6123cc5f46c02b3c6dd04a Mon Sep 17 00:00:00 2001
From: Pavel Raiskup <prais...@redhat.com>
Date: Thu, 30 Mar 2017 13:30:15 +0200
Subject: [PATCH] Fix non-deterministic archive type detection
Due to analysis of partly uninitialized read-ahead buffer
(short_read call), we sometimes mistakenly classified very small
compressed archives as non-compressed; which in turn caused
extraction failure.
* src/buffer.c (check_compressed_archive): Don't assume that
archives smaller than BLOCKSIZE could be non-compressed, as tar
header always has at least one block.
---
src/buffer.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/src/buffer.c b/src/buffer.c
index fb34834..f064d2a 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -391,10 +391,12 @@ check_compressed_archive (bool *pshort)
/* Restore global values */
read_full_records = sfr;
- if ((strcmp (record_start->header.magic, TMAGIC) == 0 ||
- strcmp (record_start->buffer + offsetof (struct posix_header, magic),
- OLDGNU_MAGIC) == 0) &&
- tar_checksum (record_start, true) == HEADER_SUCCESS)
+ if (record_start != record_end /* no files smaller than BLOCKSIZE */
+ && (strcmp (record_start->header.magic, TMAGIC) == 0
+ || strcmp (record_start->buffer + offsetof (struct posix_header,
+ magic),
+ OLDGNU_MAGIC) == 0)
+ && tar_checksum (record_start, true) == HEADER_SUCCESS)
/* Probably a valid header */
return ct_tar;
--
2.9.3
