From 3c2a2cd94d3b062aa5bf850b82364039ec9c6029 Mon Sep 17 00:00:00 2001 From: Sergey Poznyakoff Date: Fri, 21 Dec 2018 14:18:14 +0200 Subject: [PATCH 38/58] Disallow modifications to the global pax extended header in update mode. Updating global headers in update mode is not possible, because: 1) If the original archive was not in PAX format, writing the global header would overwrite first member header (and eventually data blocks) in the archive. 2) Otherwise, using the --pax-option can make the updated header occupy more blocks than the original one, which would lead to the same effect as in 1. This also fixes http://lists.gnu.org/archive/html/bug-tar/2018-12/msg00007.html * src/xheader.c (xheader_forbid_global): New function. * src/common.h (xheader_forbid_global): New prototype. * src/update.c (update_archive): Use xheader_forbid_global, instead of trying to write global extended header record. --- src/common.h | 1 + src/update.c | 2 +- src/xheader.c | 8 ++++++++ 3 files changed, 10 insertions(+), 1 deletion(-) diff --git a/src/common.h b/src/common.h index 32e6f8b..885169f 100644 --- a/src/common.h +++ b/src/common.h @@ -836,6 +836,7 @@ void xheader_store (char const *keyword, struct tar_stat_info *st, void xheader_read (struct xheader *xhdr, union block *header, off_t size); void xheader_write (char type, char *name, time_t t, struct xheader *xhdr); void xheader_write_global (struct xheader *xhdr); +void xheader_forbid_global (void); void xheader_finish (struct xheader *hdr); void xheader_destroy (struct xheader *hdr); char *xheader_xhdr_name (struct tar_stat_info *st); diff --git a/src/update.c b/src/update.c index 2f823e4..4aa4ac6 100644 --- a/src/update.c +++ b/src/update.c @@ -111,7 +111,7 @@ update_archive (void) name_gather (); open_archive (ACCESS_UPDATE); - buffer_write_global_xheader (); + xheader_forbid_global (); while (!found_end) { diff --git a/src/xheader.c b/src/xheader.c index e938502..010cab7 100644 --- a/src/xheader.c +++ b/src/xheader.c @@ -469,6 +469,14 @@ xheader_write_global (struct xheader *xhdr) } } +/* Forbid modifications of the global extended header */ +void +xheader_forbid_global (void) +{ + if (keyword_global_override_list) + USAGE_ERROR ((0, 0, _("can't update global extended header record"))); +} + void xheader_xattr_init (struct tar_stat_info *st) { -- 2.19.1