* Unused local variable load_addr in load_elf_binary()
@ 2021-12-06 15:46 Lukas Bulwahn
2021-12-07 0:01 ` Akira Kawata
2021-12-07 2:04 ` Kees Cook
0 siblings, 2 replies; 4+ messages in thread
From: Lukas Bulwahn @ 2021-12-06 15:46 UTC (permalink / raw)
To: Akira Kawata
Cc: Alexey Dobriyan, Alexander Viro, Eric Biederman, Kees Cook,
Andrew Morton, linux-fsdevel, Linux Kernel Mailing List,
kernel-janitors
Dear Akira-san,
With commit 0c9333606e30 ("fs/binfmt_elf: Fix AT_PHDR for unusual ELF
files"), you have changed load_elf_binary() in ./fs/binfmt_elf.c in a
way such that the local variable load_addr in load_elf_binary() is not
used anymore.
I had a quick look at the code and I think the following refactoring
would be good:
1. Remove the definition of load_addr and its unneeded computation of load_addr
2. Rename load_addr_set to first (or a similar name) to represent that
this variable is not linked to the non-existing load_addr, but states
that it captures the first iteration of the loop. Note that first has
the inverse meaning of load_addr_set.
The issue was reported by make clang-analyzer:
./fs/binfmt_elf.c:1167:5: warning: Value stored to 'load_addr' is
never read [clang-analyzer-deadcode.DeadStores]
load_addr += load_bias;
^ ~~~~~~~~~
Best regards,
Lukas
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: Unused local variable load_addr in load_elf_binary()
2021-12-06 15:46 Unused local variable load_addr in load_elf_binary() Lukas Bulwahn
@ 2021-12-07 0:01 ` Akira Kawata
2021-12-07 2:04 ` Kees Cook
1 sibling, 0 replies; 4+ messages in thread
From: Akira Kawata @ 2021-12-07 0:01 UTC (permalink / raw)
To: Lukas Bulwahn
Cc: Alexey Dobriyan, Alexander Viro, Eric Biederman, Kees Cook,
Andrew Morton, linux-fsdevel, Linux Kernel Mailing List,
kernel-janitors
On Mon, Dec 06, 2021 at 04:46:01PM +0100, Lukas Bulwahn wrote:
> Dear Akira-san,
>
> With commit 0c9333606e30 ("fs/binfmt_elf: Fix AT_PHDR for unusual ELF
> files"), you have changed load_elf_binary() in ./fs/binfmt_elf.c in a
> way such that the local variable load_addr in load_elf_binary() is not
> used anymore.
>
> I had a quick look at the code and I think the following refactoring
> would be good:
>
> 1. Remove the definition of load_addr and its unneeded computation of load_addr
>
> 2. Rename load_addr_set to first (or a similar name) to represent that
> this variable is not linked to the non-existing load_addr, but states
> that it captures the first iteration of the loop. Note that first has
> the inverse meaning of load_addr_set.
>
> The issue was reported by make clang-analyzer:
>
> ./fs/binfmt_elf.c:1167:5: warning: Value stored to 'load_addr' is
> never read [clang-analyzer-deadcode.DeadStores]
> load_addr += load_bias;
> ^ ~~~~~~~~~
>
>
> Best regards,
>
> Lukas
Thank you for your comments. Should I send a new patch, or change
the existing patch in linux-next?
Akira
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: Unused local variable load_addr in load_elf_binary()
2021-12-06 15:46 Unused local variable load_addr in load_elf_binary() Lukas Bulwahn
2021-12-07 0:01 ` Akira Kawata
@ 2021-12-07 2:04 ` Kees Cook
2021-12-07 3:23 ` Akira Kawata
1 sibling, 1 reply; 4+ messages in thread
From: Kees Cook @ 2021-12-07 2:04 UTC (permalink / raw)
To: Lukas Bulwahn
Cc: Akira Kawata, Alexey Dobriyan, Alexander Viro, Eric Biederman,
Andrew Morton, linux-fsdevel, Linux Kernel Mailing List,
kernel-janitors
On Mon, Dec 06, 2021 at 04:46:01PM +0100, Lukas Bulwahn wrote:
> Dear Akira-san,
>
> With commit 0c9333606e30 ("fs/binfmt_elf: Fix AT_PHDR for unusual ELF
> files"), you have changed load_elf_binary() in ./fs/binfmt_elf.c in a
> way such that the local variable load_addr in load_elf_binary() is not
> used anymore.
EEk! yeah, this totally broke ELF randomization. this needs to be
entirely reverted.
--
Kees Cook
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: Unused local variable load_addr in load_elf_binary()
2021-12-07 2:04 ` Kees Cook
@ 2021-12-07 3:23 ` Akira Kawata
0 siblings, 0 replies; 4+ messages in thread
From: Akira Kawata @ 2021-12-07 3:23 UTC (permalink / raw)
To: Kees Cook
Cc: Lukas Bulwahn, Alexey Dobriyan, Alexander Viro, Eric Biederman,
Andrew Morton, linux-fsdevel, Linux Kernel Mailing List,
kernel-janitors
On Mon, Dec 06, 2021 at 06:04:56PM -0800, Kees Cook wrote:
> On Mon, Dec 06, 2021 at 04:46:01PM +0100, Lukas Bulwahn wrote:
> > Dear Akira-san,
> >
> > With commit 0c9333606e30 ("fs/binfmt_elf: Fix AT_PHDR for unusual ELF
> > files"), you have changed load_elf_binary() in ./fs/binfmt_elf.c in a
> > way such that the local variable load_addr in load_elf_binary() is not
> > used anymore.
>
> EEk! yeah, this totally broke ELF randomization. this needs to be
> entirely reverted.
>
> --
> Kees Cook
I think my patch doesn't affect on ELF randomization because it keeps
the way of load_addr calculation.
Akira Kawata
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-12-07 3:23 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
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2021-12-06 15:46 Unused local variable load_addr in load_elf_binary() Lukas Bulwahn
2021-12-07 0:01 ` Akira Kawata
2021-12-07 2:04 ` Kees Cook
2021-12-07 3:23 ` Akira Kawata
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