* [PATCH 1/2] modpost: fix potential segmentation fault for addend_i386_rel()
@ 2020-05-25 5:47 Masahiro Yamada
2020-05-25 5:47 ` [PATCH 2/2] modpost: refactor sech_name() Masahiro Yamada
0 siblings, 1 reply; 2+ messages in thread
From: Masahiro Yamada @ 2020-05-25 5:47 UTC (permalink / raw)
To: linux-kbuild; +Cc: Masahiro Yamada, Michal Marek, linux-kernel
This may not be a practical problem, but the second pass of ARCH=i386
modpost causes segmentation fault if the -s option is not passed.
MODPOST 12 modules
Segmentation fault (core dumped)
make[2]: *** [scripts/Makefile.modpost:94: __modpost] Error 139
make[1]: *** [Makefile:1339: modules] Error 2
make[1]: *** Waiting for unfinished jobs....
The segmentation fault occurs when section_rel() is called for vmlinux,
which is untested in regular builds. The cause of the problem is
reloc_location() returns a wrong pointer for ET_EXEC object type.
In this case, you need to subtract sechdr->sh_addr, otherwise it would
get access beyond the mmap'ed memory.
Add sym_get_data_offset() helper to avoid code duplication.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---
scripts/mod/modpost.c | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 34f2aa3a021f..a8306adb3554 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -345,19 +345,23 @@ static const char *sec_name(struct elf_info *elf, int secindex)
return sech_name(elf, &elf->sechdrs[secindex]);
}
-static void *sym_get_data(const struct elf_info *info, const Elf_Sym *sym)
+static void *sym_get_data_offset(const struct elf_info *info,
+ unsigned int secindex, unsigned long offset)
{
- unsigned int secindex = get_secindex(info, sym);
Elf_Shdr *sechdr = &info->sechdrs[secindex];
- unsigned long offset;
- offset = sym->st_value;
if (info->hdr->e_type != ET_REL)
offset -= sechdr->sh_addr;
return (void *)info->hdr + sechdr->sh_offset + offset;
}
+static void *sym_get_data(const struct elf_info *info, const Elf_Sym *sym)
+{
+ return sym_get_data_offset(info, get_secindex(info, sym),
+ sym->st_value);
+}
+
#define strstarts(str, prefix) (strncmp(str, prefix, strlen(prefix)) == 0)
static enum export export_from_secname(struct elf_info *elf, unsigned int sec)
@@ -1761,11 +1765,7 @@ static void check_section_mismatch(const char *modname, struct elf_info *elf,
static unsigned int *reloc_location(struct elf_info *elf,
Elf_Shdr *sechdr, Elf_Rela *r)
{
- Elf_Shdr *sechdrs = elf->sechdrs;
- int section = sechdr->sh_info;
-
- return (void *)elf->hdr + sechdrs[section].sh_offset +
- r->r_offset;
+ return sym_get_data_offset(elf, sechdr->sh_info, r->r_offset);
}
static int addend_386_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
--
2.25.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [PATCH 2/2] modpost: refactor sech_name()
2020-05-25 5:47 [PATCH 1/2] modpost: fix potential segmentation fault for addend_i386_rel() Masahiro Yamada
@ 2020-05-25 5:47 ` Masahiro Yamada
0 siblings, 0 replies; 2+ messages in thread
From: Masahiro Yamada @ 2020-05-25 5:47 UTC (permalink / raw)
To: linux-kbuild; +Cc: Masahiro Yamada, Michal Marek, linux-kernel
Use sym_get_data_offset() helper to get access to the .shstrtab
section data. No functional change is intended because
elf->sechdrs[elf->secindex_strings].sh_addr is 0 for both ET_REL
and ET_EXEC object types.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---
scripts/mod/modpost.c | 22 ++++++++++------------
1 file changed, 10 insertions(+), 12 deletions(-)
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index a8306adb3554..a5f3908bc9e4 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -333,18 +333,6 @@ static enum export export_no(const char *s)
return export_unknown;
}
-static const char *sech_name(struct elf_info *elf, Elf_Shdr *sechdr)
-{
- return (void *)elf->hdr +
- elf->sechdrs[elf->secindex_strings].sh_offset +
- sechdr->sh_name;
-}
-
-static const char *sec_name(struct elf_info *elf, int secindex)
-{
- return sech_name(elf, &elf->sechdrs[secindex]);
-}
-
static void *sym_get_data_offset(const struct elf_info *info,
unsigned int secindex, unsigned long offset)
{
@@ -362,6 +350,16 @@ static void *sym_get_data(const struct elf_info *info, const Elf_Sym *sym)
sym->st_value);
}
+static const char *sech_name(struct elf_info *elf, Elf_Shdr *sechdr)
+{
+ return sym_get_data_offset(elf, elf->secindex_strings, sechdr->sh_name);
+}
+
+static const char *sec_name(struct elf_info *elf, int secindex)
+{
+ return sech_name(elf, &elf->sechdrs[secindex]);
+}
+
#define strstarts(str, prefix) (strncmp(str, prefix, strlen(prefix)) == 0)
static enum export export_from_secname(struct elf_info *elf, unsigned int sec)
--
2.25.1
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