Hi Anton,
On Thu, Feb 13, 2025 at 07:33:12PM +0300, Anton Moryakov wrote:
> Static analyzer reported:
> Return value of a function 'elf_strptr' is dereferenced at readelf.c:7171
> without checking for NULL, but it is usually checked for this function
> (71/74).
>
> Corrections explained:
> - Added a NULL check for the scnname variable, which contains the result of
> the elf_strptr call.
> - The check is placed before the first use of scnname to prevent dereferencing
> a NULL pointer.
Yes, I see why a static analyzer might assume that. But if you look
at the caller of print_debug_frame_section, the function print_debug,
then you'll see that it already does this check (at line 12140):
const char *name = elf_strptr (ebl->elf, shstrndx,
shdr->sh_name);
if (name == NULL)
continue;
And at the start of print_debug_frame_section we do have:
/* We know this call will succeed since it did in the caller. */
(void) elf_getshdrstrndx (ebl->elf, &shstrndx);
const char *scnname = elf_strptr (ebl->elf, shstrndx, shdr->sh_name);
So I don't think scnname can be NULL.
But this code is different from any other print_debug_* code. All
other code uses section_name (Ebl *ebl, GElf_Shdr *shdr) to get the
section name.
So what we could do to make the static analyzer happy is simply do the
same here. I pushed the attached.
Cheers,
Mark
>From dfa7b2c23ddabcba2a4972fa67d3c670ae31f1ee Mon Sep 17 00:00:00 2001
From: Mark Wielaard <[email protected]>
Date: Thu, 27 Feb 2025 21:22:49 +0100
Subject: [PATCH] readelf: Use section_name instead of elf_strptr in
print_debug_frame_section
All other print_debug_* functions use section_name (ebl, shdr) to get
the current section name. Be consistent and use the same method in
print_debug_frame_section to make static analyzers happy who might
think elf_strptr can return NULL in this case.
* src/readelf.c (print_debug_frame_section): Use section_name
instead of elf_strptr to get the section name.
Signed-off-by: Mark Wielaard <[email protected]>
---
src/readelf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/readelf.c b/src/readelf.c
index 61d5b71a7913..c9aebd5b3e5f 100644
--- a/src/readelf.c
+++ b/src/readelf.c
@@ -7170,7 +7170,7 @@ print_debug_frame_section (Dwfl_Module *dwflmod, Ebl
*ebl, GElf_Ehdr *ehdr,
size_t shstrndx;
/* We know this call will succeed since it did in the caller. */
(void) elf_getshdrstrndx (ebl->elf, &shstrndx);
- const char *scnname = elf_strptr (ebl->elf, shstrndx, shdr->sh_name);
+ const char *scnname = section_name (ebl, shdr);
/* Needed if we find PC-relative addresses. */
GElf_Addr bias;
--
2.48.1
