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SubjectRe: [PATCH] binfmt_elf_fdpic: Fix clear_user() error handling
David Howells <dhowells@redhat.com> wrote:

> From: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
>

Thanks for updating, improving, the explanation!

Takuya


> clear_user() returns the number of bytes that could not be copied rather than
> an error code. So we should return -EFAULT rather than directly returning the
> results.
>
> Without this patch, positive values may be returned to elf_fdpic_map_file()
> and the following error handlings do not function as expected.
>
> 1.
> ret = elf_fdpic_map_file_constdisp_on_uclinux(params, file, mm);
> if (ret < 0)
> return ret;
> 2.
> ret = elf_fdpic_map_file_by_direct_mmap(params, file, mm);
> if (ret < 0)
> return ret;
>
> Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
> Signed-off-by: David Howells <dhowells@redhat.com>
> Acked-by: Mike Frysinger <vapier@gentoo.org>
> CC: Alexander Viro <viro@zeniv.linux.org.uk>
> CC: Andrew Morton <akpm@linux-foundation.org>
> CC: Daisuke HATAYAMA <d.hatayama@jp.fujitsu.com>
> CC: Paul Mundt <lethal@linux-sh.org>
> ---
>
> fs/binfmt_elf_fdpic.c | 26 +++++++++++---------------
> 1 files changed, 11 insertions(+), 15 deletions(-)
>
>
> diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
> index 2c5f9a0..63039ed 100644
> --- a/fs/binfmt_elf_fdpic.c
> +++ b/fs/binfmt_elf_fdpic.c
> @@ -990,10 +990,9 @@ static int elf_fdpic_map_file_constdisp_on_uclinux(
>
> /* clear any space allocated but not loaded */
> if (phdr->p_filesz < phdr->p_memsz) {
> - ret = clear_user((void *) (seg->addr + phdr->p_filesz),
> - phdr->p_memsz - phdr->p_filesz);
> - if (ret)
> - return ret;
> + if (clear_user((void *) (seg->addr + phdr->p_filesz),
> + phdr->p_memsz - phdr->p_filesz))
> + return -EFAULT;
> }
>
> if (mm) {
> @@ -1027,7 +1026,7 @@ static int elf_fdpic_map_file_by_direct_mmap(struct elf_fdpic_params *params,
> struct elf32_fdpic_loadseg *seg;
> struct elf32_phdr *phdr;
> unsigned long load_addr, delta_vaddr;
> - int loop, dvset, ret;
> + int loop, dvset;
>
> load_addr = params->load_addr;
> delta_vaddr = 0;
> @@ -1127,9 +1126,8 @@ static int elf_fdpic_map_file_by_direct_mmap(struct elf_fdpic_params *params,
> * PT_LOAD */
> if (prot & PROT_WRITE && disp > 0) {
> kdebug("clear[%d] ad=%lx sz=%lx", loop, maddr, disp);
> - ret = clear_user((void __user *) maddr, disp);
> - if (ret)
> - return ret;
> + if (clear_user((void __user *) maddr, disp))
> + return -EFAULT;
> maddr += disp;
> }
>
> @@ -1164,19 +1162,17 @@ static int elf_fdpic_map_file_by_direct_mmap(struct elf_fdpic_params *params,
> if (prot & PROT_WRITE && excess1 > 0) {
> kdebug("clear[%d] ad=%lx sz=%lx",
> loop, maddr + phdr->p_filesz, excess1);
> - ret = clear_user((void __user *) maddr + phdr->p_filesz,
> - excess1);
> - if (ret)
> - return ret;
> + if (clear_user((void __user *) maddr + phdr->p_filesz,
> + excess1))
> + return -EFAULT;
> }
>
> #else
> if (excess > 0) {
> kdebug("clear[%d] ad=%lx sz=%lx",
> loop, maddr + phdr->p_filesz, excess);
> - ret = clear_user((void *) maddr + phdr->p_filesz, excess);
> - if (ret)
> - return ret;
> + if (clear_user((void *) maddr + phdr->p_filesz, excess))
> + return -EFAULT;
> }
> #endif
>
>


--
Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>


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