[COMMITTED] libdwfl: Don't read beyond end of file in dwfl_segment_report_module

[Mark Wielaard <mark@klomp.org>]

The ELF might not be fully mapped into memory (which probably means
the phdrs are bogus). Don't try to read beyond what we have in memory
already.

Reported-by: Evgeny Vereshchagin <evvers@ya.ru>
Signed-off-by: Mark Wielaard <mark@klomp.org>
---
 libdwfl/ChangeLog                    | 5 +++++
 libdwfl/dwfl_segment_report_module.c | 6 +++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
index 57b2c494..b2a8752a 100644
--- a/libdwfl/ChangeLog
+++ b/libdwfl/ChangeLog
@@ -1,3 +1,8 @@
+2021-12-08  Mark Wielaard  <mark@klomp.org>
+
+	* dwfl_segment_report_module.c (dwfl_segment_report_module): Don't
+	read beyond of (actual) end of (memory) file.
+
 2021-11-18  Matthias Maennich  <maennich@google.com>
 
 	* linux-kernel-modules.c (dwfl_linux_kernel_report_modules):
diff --git a/libdwfl/dwfl_segment_report_module.c b/libdwfl/dwfl_segment_report_module.c
index ee9cfa2e..f6a1799e 100644
--- a/libdwfl/dwfl_segment_report_module.c
+++ b/libdwfl/dwfl_segment_report_module.c
@@ -924,8 +924,12 @@ dwfl_segment_report_module (Dwfl *dwfl, int ndx, const char *name,
               GElf_Off offset = is32 ? p32[i].p_offset : p64[i].p_offset;
               GElf_Xword filesz = is32 ? p32[i].p_filesz : p64[i].p_filesz;
 
+              /* Don't try to read beyond the actual end of file.  */
+              if (offset >= file_trimmed_end)
+                continue;
+
               void *into = contents + offset;
-              size_t read_size = filesz;
+              size_t read_size = MIN (filesz, file_trimmed_end - offset);
               (*memory_callback) (dwfl, addr_segndx (dwfl, segment,
                                                      vaddr + bias, false),
                                   &into, &read_size, vaddr + bias, read_size,
-- 
2.18.4