From 874a1c8c32036f790fa527acfab3f6f18740f089 Mon Sep 17 00:00:00 2001 From: Antoine Tremblay Date: Thu, 26 Jan 2017 10:47:27 -0500 Subject: [PATCH] Fix crash when loading a core with unexpected register section size 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=, regcache=0x2c26260, regno=) 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 4e85fcdc5ce..ce3f317c057 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2017-01-26 Antoine Tremblay + + * corelow.c (get_core_register_section): Check for regset + existence before checking for REGSET_VARIABLE_SIZE. + 2017-01-26 Yao Qi Pedro Alves diff --git a/gdb/corelow.c b/gdb/corelow.c index a075d9e1319..ecde9542b55 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); -- 2.30.2