* [PATCH] libelf: Only set shdr state when there is at least one shdr
@ 2021-12-19 14:57 Mark Wielaard
0 siblings, 0 replies; only message in thread
From: Mark Wielaard @ 2021-12-19 14:57 UTC (permalink / raw)
To: elfutils-devel; +Cc: Mark Wielaard
The elf shdr state only needs to be set when scncnt is at least
one. Otherwise e_shoff can be bogus. Also use unsigned arithmetic for
checking e_shoff alignment.
Signed-off-by: Mark Wielaard <mark@klomp.org>
---
libelf/ChangeLog | 5 +++++
libelf/elf_begin.c | 16 ++++++++++------
2 files changed, 15 insertions(+), 6 deletions(-)
diff --git a/libelf/ChangeLog b/libelf/ChangeLog
index 617d97a5..29a8aae1 100644
--- a/libelf/ChangeLog
+++ b/libelf/ChangeLog
@@ -1,3 +1,8 @@
+2021-12-19 Mark Wielaard <mark@klomp.org>
+
+ * elf_begin.c (file_read_elf): Cast ehdr to uintptr_t before e_shoff
+ alignment check. Only set shdr state when scncnt is larger than zero.
+
2021-12-16 Mark Wielaard <mark@klomp.org>
* libelfP.h (NOTE_ALIGN4): And with negative unsigned long.
diff --git a/libelf/elf_begin.c b/libelf/elf_begin.c
index bd3399de..0c9a988d 100644
--- a/libelf/elf_begin.c
+++ b/libelf/elf_begin.c
@@ -383,7 +383,7 @@ file_read_elf (int fildes, void *map_address, unsigned char *e_ident,
if (map_address != NULL && e_ident[EI_DATA] == MY_ELFDATA
&& cmd != ELF_C_READ_MMAP /* We need a copy to be able to write. */
&& (ALLOW_UNALIGNED
- || (((uintptr_t) ((char *) ehdr + e_shoff)
+ || ((((uintptr_t) ehdr + e_shoff)
& (__alignof__ (Elf32_Shdr) - 1)) == 0)))
{
if (unlikely (scncnt > 0 && e_shoff >= maxsize)
@@ -395,8 +395,10 @@ file_read_elf (int fildes, void *map_address, unsigned char *e_ident,
__libelf_seterrno (ELF_E_INVALID_ELF);
return NULL;
}
- elf->state.elf32.shdr
- = (Elf32_Shdr *) ((char *) ehdr + e_shoff);
+
+ if (scncnt > 0)
+ elf->state.elf32.shdr
+ = (Elf32_Shdr *) ((char *) ehdr + e_shoff);
for (size_t cnt = 0; cnt < scncnt; ++cnt)
{
@@ -485,15 +487,17 @@ file_read_elf (int fildes, void *map_address, unsigned char *e_ident,
if (map_address != NULL && e_ident[EI_DATA] == MY_ELFDATA
&& cmd != ELF_C_READ_MMAP /* We need a copy to be able to write. */
&& (ALLOW_UNALIGNED
- || (((uintptr_t) ((char *) ehdr + e_shoff)
+ || ((((uintptr_t) ehdr + e_shoff)
& (__alignof__ (Elf64_Shdr) - 1)) == 0)))
{
if (unlikely (scncnt > 0 && e_shoff >= maxsize)
|| unlikely (maxsize - e_shoff
< scncnt * sizeof (Elf64_Shdr)))
goto free_and_out;
- elf->state.elf64.shdr
- = (Elf64_Shdr *) ((char *) ehdr + e_shoff);
+
+ if (scncnt > 0)
+ elf->state.elf64.shdr
+ = (Elf64_Shdr *) ((char *) ehdr + e_shoff);
for (size_t cnt = 0; cnt < scncnt; ++cnt)
{
--
2.30.2
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