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commit cf8c6a634c0a04a9f5d198ef05310f85f7338839
Author: Florian Weimer <fweimer@redhat.com>
Date: Fri Nov 5 17:01:24 2021 +0100
elf: Earlier missing dynamic segment check in _dl_map_object_from_fd
Separated debuginfo files have PT_DYNAMIC with p_filesz == 0. We
need to check for that before the _dl_map_segments call because
that could attempt to write to mappings that extend beyond the end
of the file, resulting in SIGBUS.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
(cherry picked from commit ea32ec354c65ddad11b82ca9d057010df13a9cea)
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 4445c28ef3fb4a7e..0976977fbdf21902 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -1130,6 +1130,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
struct loadcmd loadcmds[l->l_phnum];
size_t nloadcmds = 0;
bool has_holes = false;
+ bool empty_dynamic = false;
/* The struct is initialized to zero so this is not necessary:
l->l_ld = 0;
@@ -1142,7 +1143,9 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
segments are mapped in. We record the addresses it says
verbatim, and later correct for the run-time load address. */
case PT_DYNAMIC:
- if (ph->p_filesz)
+ if (ph->p_filesz == 0)
+ empty_dynamic = true; /* Usually separate debuginfo. */
+ else
{
/* Debuginfo only files from "objcopy --only-keep-debug"
contain a PT_DYNAMIC segment with p_filesz == 0. Skip
@@ -1265,6 +1268,13 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
goto lose;
}
+ /* This check recognizes most separate debuginfo files. */
+ if (__glibc_unlikely ((l->l_ld == 0 && type == ET_DYN) || empty_dynamic))
+ {
+ errstring = N_("object file has no dynamic section");
+ goto lose;
+ }
+
/* Length of the sections to be loaded. */
maplength = loadcmds[nloadcmds - 1].allocend - loadcmds[0].mapstart;
@@ -1282,15 +1292,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
}
}
- if (l->l_ld == 0)
- {
- if (__glibc_unlikely (type == ET_DYN))
- {
- errstring = N_("object file has no dynamic section");
- goto lose;
- }
- }
- else
+ if (l->l_ld != 0)
l->l_ld = (ElfW(Dyn) *) ((ElfW(Addr)) l->l_ld + l->l_addr);
elf_get_dynamic_info (l);