[bug report] modpost: handle relocations mismatch in __ex_table.

[bug report] modpost: handle relocations mismatch in __ex_table.

[Dan Carpenter]

[ Ancient code warning. - dan ]

Hello Quentin Casasnovas,

The patch 52dc0595d540: "modpost: handle relocations mismatch in
__ex_table." from Apr 13, 2015, leads to the following Smatch static
checker warning:

	./scripts/mod/modpost.c:1154 is_executable_section()
	warn: array off by one? 'elf->sechdrs[secndx]'

./scripts/mod/modpost.c
    1149 static bool is_executable_section(struct elf_info *elf, unsigned int secndx)
    1150 {
    1151         if (secndx > elf->num_sections)
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^
I'm not positive, but I think this should be >=.

    1152                 return false;
    1153 
--> 1154         return (elf->sechdrs[secndx].sh_flags & SHF_EXECINSTR) != 0;
                                      ^^^^^^
out of bounds read.

    1155 }

regards,
dan carpenter

Re: [bug report] modpost: handle relocations mismatch in __ex_table.

[Masahiro Yamada]

On Tue, Jun 6, 2023 at 5:31 PM Dan Carpenter <dan.carpenter@linaro.org> wrote:
>
> [ Ancient code warning. - dan ]
>
> Hello Quentin Casasnovas,
>
> The patch 52dc0595d540: "modpost: handle relocations mismatch in
> __ex_table." from Apr 13, 2015, leads to the following Smatch static
> checker warning:
>
>         ./scripts/mod/modpost.c:1154 is_executable_section()
>         warn: array off by one? 'elf->sechdrs[secndx]'
>
> ./scripts/mod/modpost.c
>     1149 static bool is_executable_section(struct elf_info *elf, unsigned int secndx)
>     1150 {
>     1151         if (secndx > elf->num_sections)
>                      ^^^^^^^^^^^^^^^^^^^^^^^^^^
> I'm not positive, but I think this should be >=.


Ah, right. This is a bug, and your fix is correct.





>
>     1152                 return false;
>     1153
> --> 1154         return (elf->sechdrs[secndx].sh_flags & SHF_EXECINSTR) != 0;
>                                       ^^^^^^
> out of bounds read.
>
>     1155 }
>
> regards,
> dan carpenter






-- 
Best Regards
Masahiro Yamada

Re: [bug report] modpost: handle relocations mismatch in __ex_table.

[Quentin Casasnovas]

[-- Attachment #1: Type: text/plain, Size: 1085 bytes --]

On Tue, Jun 06, 2023 at 11:31:00AM +0300, Dan Carpenter wrote:
> [ Ancient code warning. - dan ]
> 
> Hello Quentin Casasnovas,
> 
> The patch 52dc0595d540: "modpost: handle relocations mismatch in
> __ex_table." from Apr 13, 2015, leads to the following Smatch static
> checker warning:
> 
> 	./scripts/mod/modpost.c:1154 is_executable_section()
> 	warn: array off by one? 'elf->sechdrs[secndx]'
> 
> ./scripts/mod/modpost.c
>     1149 static bool is_executable_section(struct elf_info *elf, unsigned int secndx)
>     1150 {
>     1151         if (secndx > elf->num_sections)
>                      ^^^^^^^^^^^^^^^^^^^^^^^^^^
> I'm not positive, but I think this should be >=.
> 
>     1152                 return false;
>     1153 
> --> 1154         return (elf->sechdrs[secndx].sh_flags & SHF_EXECINSTR) != 0;
>                                       ^^^^^^
> out of bounds read.
> 

Oops, that is embarassing - thanks for catching that!

Have you already prepared a fix or shall I send it over?

Q


>     1155 }
> 
> regards,
> dan carpenter

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

Re: [bug report] modpost: handle relocations mismatch in __ex_table.

[Dan Carpenter]

On Mon, Jun 12, 2023 at 11:37:00AM +0200, Quentin Casasnovas wrote:
> 
> Have you already prepared a fix or shall I send it over?
> 

I sent the fix on Thursday and Masahiro Yamada already applied it.  I
Cc'd you but probably you're like me and respond to email in the order
it's recieved?

https://lore.kernel.org/all/CAK7LNATWmtiQdtvGLYL5b0Pyg4Bnmj0_Hn8xtWLzMJ_1oxkThA@mail.gmail.com/

regards,
dan carpenter

Re: [bug report] modpost: handle relocations mismatch in __ex_table.

[Quentin Casasnovas]

[-- Attachment #1: Type: text/plain, Size: 469 bytes --]

On Mon, Jun 12, 2023 at 12:51:40PM +0300, Dan Carpenter wrote:
> On Mon, Jun 12, 2023 at 11:37:00AM +0200, Quentin Casasnovas wrote:
> > 
> > Have you already prepared a fix or shall I send it over?
> > 
> 
> I sent the fix on Thursday and Masahiro Yamada already applied it.  I
> Cc'd you but probably you're like me and respond to email in the order
> it's recieved?
> 

Indeed, I just cleaned up my mailbox and saw your patch.  Thanks for the
fix!

Q

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]