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[pushed][PATCH v2] Fix crash when loading a core with unexpected register section size
- From: Antoine Tremblay <antoine dot tremblay at ericsson dot com>
- To: <gdb-patches at sourceware dot org>, <palves at redhat dot com>
- Cc: Antoine Tremblay <antoine dot tremblay at ericsson dot com>
- Date: Thu, 26 Jan 2017 10:52:55 -0500
- Subject: [pushed][PATCH v2] Fix crash when loading a core with unexpected register section size
- Authentication-results: sourceware.org; auth=none
- References: <379390ed-98c6-fb7b-b217-b768e435bf5e@redhat.com>
When loading a core without an executable like so:
$ gdb --core core
for example often the gdbarch won't contain the
iterate_over_regset_sections method. For example on ARM.
This will generate a call to get_core_register_section with a NULL regset
like at corelow.c:628
get_core_register_section (regcache, NULL, ".reg", 0, 0, "general-purpose", 1);
However a check for REGSET_VARIABLE_SIZE in get_core_register_section
assumes that regset is != NULL thus leading to a crash with this backtrace:
(gdb) bt
#0 0x000000000065907b in get_core_register_section
(regcache=regcache@entry=0x2c26260, regset=regset@entry=0x0,
name=name@entry=0xdbf7b2 ".reg", min_size=min_size@entry=0,
which=which@entry=0, human_name=human_name@entry=0xdbac28
"general-purpose", required=1)
at ../../gdb/corelow.c:542
#1 0x0000000000659b70 in get_core_registers (ops=<optimized out>,
regcache=0x2c26260, regno=<optimized out>) at ../../gdb/corelow.c:628
#2 0x000000000076e5fb in target_fetch_registers
(regcache=regcache@entry=0x2c26260, regno=regno@entry=15)
at ../../gdb/target.c:3590
Note that commit: f962539ad23759 ("Warn if core file register
section is larger than expected") introduced this issue.
Thus releases > 7.8.2 are affected.
Also, this would have been caught by gdb.base/corefile.exp but the
problem is that this triggers only if the core dump is missing some data
so that it's not recognized as a linux core dump, or it's not a linux core
dump and the core file register section is larger than expected.
So if you just create a core and read it on linux with ARM the osabi is
detected properly and iterate_over_regset_sections is present and so the
problem is not triggered.
Thus creating a linux test for this with a crafted core that meets the
problem requirements is non-trivial.
This patch fixes this crash by adding a check for regset existence before
running the condition.
gdb/ChangeLog:
* corelow.c (get_core_register_section): Check for regset
existence before checking for REGSET_VARIABLE_SIZE.
---
gdb/ChangeLog | 5 +++++
gdb/corelow.c | 4 +++-
2 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 4e85fcd..ce3f317 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2017-01-26 Antoine Tremblay <antoine.tremblay@ericsson.com>
+
+ * corelow.c (get_core_register_section): Check for regset
+ existence before checking for REGSET_VARIABLE_SIZE.
+
2017-01-26 Yao Qi <yao.qi@linaro.org>
Pedro Alves <palves@redhat.com>
diff --git a/gdb/corelow.c b/gdb/corelow.c
index a075d9e..ecde954 100644
--- a/gdb/corelow.c
+++ b/gdb/corelow.c
@@ -515,6 +515,8 @@ get_core_register_section (struct regcache *regcache,
struct bfd_section *section;
bfd_size_type size;
char *contents;
+ bool variable_size_section = (regset != NULL
+ && regset->flags & REGSET_VARIABLE_SIZE);
xfree (section_name);
@@ -539,7 +541,7 @@ get_core_register_section (struct regcache *regcache,
warning (_("Section `%s' in core file too small."), section_name);
return;
}
- if (size != min_size && !(regset->flags & REGSET_VARIABLE_SIZE))
+ if (size != min_size && !variable_size_section)
{
warning (_("Unexpected size of section `%s' in core file."),
section_name);
--
2.7.4