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SubjectRe: [PATCH 2/2] fs, elf: drop MAP_FIXED usage from elf_map
On Wed 18-04-18 19:51:05, Tetsuo Handa wrote:
> >From 0ba20dcbbc40b703413c9a6907a77968b087811b Mon Sep 17 00:00:00 2001
> From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Date: Wed, 18 Apr 2018 15:31:48 +0900
> Subject: [PATCH] fs, elf: don't complain MAP_FIXED_NOREPLACE if mapping
> failed.
>
> Commit 4ed28639519c7bad ("fs, elf: drop MAP_FIXED usage from elf_map") is
> printing spurious messages under memory pressure due to map_addr == -ENOMEM.
>
> 9794 (a.out): Uhuuh, elf segment at 00007f2e34738000(fffffffffffffff4) requested but the memory is mapped already
> 14104 (a.out): Uhuuh, elf segment at 00007f34fd76c000(fffffffffffffff4) requested but the memory is mapped already
> 16843 (a.out): Uhuuh, elf segment at 00007f930ecc7000(fffffffffffffff4) requested but the memory is mapped already

Hmm this is ENOMEM.

> Don't complain if IS_ERR_VALUE(),

this is simply wrong. We do want to warn on the failure because this is
when the actual clash happens. We should just warn on EEXIST.

> and use %px for printing the address.
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Andrei Vagin <avagin@openvz.org>
> Cc: Khalid Aziz <khalid.aziz@oracle.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
> Cc: Joel Stanley <joel@jms.id.au>
> Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
> ---
> fs/binfmt_elf.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
> index 41e0418..559d35b 100644
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -377,10 +377,10 @@ static unsigned long elf_map(struct file *filep, unsigned long addr,
> } else
> map_addr = vm_mmap(filep, addr, size, prot, type, off);
>
> - if ((type & MAP_FIXED_NOREPLACE) && BAD_ADDR(map_addr))
> - pr_info("%d (%s): Uhuuh, elf segment at %p requested but the memory is mapped already\n",
> - task_pid_nr(current), current->comm,
> - (void *)addr);
> + if ((type & MAP_FIXED_NOREPLACE) && BAD_ADDR(map_addr) &&
> + !IS_ERR_VALUE(map_addr))
> + pr_info("%d (%s): Uhuuh, elf segment at %px requested but the memory is mapped already\n",
> + task_pid_nr(current), current->comm, (void *)addr);
>
> return(map_addr);
> }
> --
> 1.8.3.1
>
>

--
Michal Hocko
SUSE Labs

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