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Re: [Xen-devel] [PATCH 04/28] libxl: fix libxl_string_list_length and its only caller



On 09/17/2013 11:37 PM, Matthew Daley wrote:
The wrong amount of indirections were being taken in
libxl_string_list_length, and its only caller was miscounting the amount
of initial non-list arguments, seemingly since the initial commit
(599c784).

This has been seen and reported in the wild (##xen):
< Trixboxer> Hi, any idea why would I get
< Trixboxer> xl: libxl_bootloader.c:42: bootloader_arg: Assertion `bl->nargs < 
bl->argsspace' failed.
< Trixboxer> 4.2.2-23.el6

Coverity-ID: 1054954
Signed-off-by: Matthew Daley<mattjd@xxxxxxxxx>
---
  tools/libxl/libxl.c            |    2 +-
  tools/libxl/libxl_bootloader.c |    2 +-
  2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 0879f23..ca24ca3 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -202,7 +202,7 @@ int libxl_string_list_length(const libxl_string_list *psl)
  {
      if (!psl) return 0;

This should be
    if (!psl || !(*psl)) return 0;

We segfault otherwise at the changed line below if no arguments are passed to the bootloader (as is the case with pvgrub).

      int i = 0;
-    while (*psl++) i++;
+    while ((*psl)[i]) i++;
      return i;
  }

(I am surprised Coverity didn't flag this)

-boris

diff --git a/tools/libxl/libxl_bootloader.c b/tools/libxl/libxl_bootloader.c
index ed12b2c..3287bf7 100644
--- a/tools/libxl/libxl_bootloader.c
+++ b/tools/libxl/libxl_bootloader.c
@@ -48,7 +48,7 @@ static void make_bootloader_args(libxl__gc *gc, 
libxl__bootloader_state *bl,
  {
      const libxl_domain_build_info *info = bl->info;
- bl->argsspace = 7 + libxl_string_list_length(&info->u.pv.bootloader_args);
+    bl->argsspace = 9 + libxl_string_list_length(&info->u.pv.bootloader_args);
GCNEW_ARRAY(bl->args, bl->argsspace);


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