Re: [PATCH 2/6] binfmt_elf: open code copy_siginfo_to_user to kernelspace buffer
On Mon, Apr 06, 2020 at 03:01:24PM +0200, Arnd Bergmann wrote:
> > static void fill_siginfo_note(struct memelfnote *note, user_siginfo_t
> > *csigdata,
> > const kernel_siginfo_t *siginfo)
> > {
> > - mm_segment_t old_fs = get_fs();
> > - set_fs(KERNEL_DS);
> > - copy_siginfo_to_user((user_siginfo_t __user *) csigdata, siginfo);
> > - set_fs(old_fs);
> > + memcpy(csigdata, siginfo, sizeof(struct kernel_siginfo));
> > + memset((char *)csigdata + sizeof(struct kernel_siginfo), 0,
> > + SI_EXPANSION_SIZE);
> > fill_note(note, "CORE", NT_SIGINFO, sizeof(*csigdata), csigdata);
> > }
>
> I think this breaks compat binfmt-elf mode, which relies on this trick:
>
> fs/compat_binfmt_elf.c:#define copy_siginfo_to_user copy_siginfo_to_user32
> fs/compat_binfmt_elf.c#include "binfmt_elf.c"
>
> At least we seem to only have one remaining implementation of
> __copy_siginfo_to_user32(), so fixing this won't require touching all
> architectures, but I don't see an obvious way to do it right. Maybe
> compat-binfmt-elf.c should just override fill_siginfo_note() itself
> rather than overriding copy_siginfo_to_user().
Ooops. Yes, this will need some manual handling.
Re: [PATCH 2/6] binfmt_elf: open code copy_siginfo_to_user to kernelspace buffer
On Mon, Apr 6, 2020 at 2:03 PM Christoph Hellwig wrote:
>
> Instead of messing with the address limit just open code the trivial
> memcpy + memset logic.
>
> Signed-off-by: Christoph Hellwig
> ---
> fs/binfmt_elf.c | 7 +++
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
> index f4713ea76e82..d744ce9a4b52 100644
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -1556,10 +1556,9 @@ static void fill_auxv_note(struct memelfnote *note,
> struct mm_struct *mm)
> static void fill_siginfo_note(struct memelfnote *note, user_siginfo_t
> *csigdata,
> const kernel_siginfo_t *siginfo)
> {
> - mm_segment_t old_fs = get_fs();
> - set_fs(KERNEL_DS);
> - copy_siginfo_to_user((user_siginfo_t __user *) csigdata, siginfo);
> - set_fs(old_fs);
> + memcpy(csigdata, siginfo, sizeof(struct kernel_siginfo));
> + memset((char *)csigdata + sizeof(struct kernel_siginfo), 0,
> + SI_EXPANSION_SIZE);
> fill_note(note, "CORE", NT_SIGINFO, sizeof(*csigdata), csigdata);
> }
I think this breaks compat binfmt-elf mode, which relies on this trick:
fs/compat_binfmt_elf.c:#define copy_siginfo_to_user copy_siginfo_to_user32
fs/compat_binfmt_elf.c#include "binfmt_elf.c"
At least we seem to only have one remaining implementation of
__copy_siginfo_to_user32(), so fixing this won't require touching all
architectures, but I don't see an obvious way to do it right. Maybe
compat-binfmt-elf.c should just override fill_siginfo_note() itself
rather than overriding copy_siginfo_to_user().
Arnd
[PATCH 2/6] binfmt_elf: open code copy_siginfo_to_user to kernelspace buffer
Instead of messing with the address limit just open code the trivial
memcpy + memset logic.
Signed-off-by: Christoph Hellwig
---
fs/binfmt_elf.c | 7 +++
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index f4713ea76e82..d744ce9a4b52 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1556,10 +1556,9 @@ static void fill_auxv_note(struct memelfnote *note,
struct mm_struct *mm)
static void fill_siginfo_note(struct memelfnote *note, user_siginfo_t
*csigdata,
const kernel_siginfo_t *siginfo)
{
- mm_segment_t old_fs = get_fs();
- set_fs(KERNEL_DS);
- copy_siginfo_to_user((user_siginfo_t __user *) csigdata, siginfo);
- set_fs(old_fs);
+ memcpy(csigdata, siginfo, sizeof(struct kernel_siginfo));
+ memset((char *)csigdata + sizeof(struct kernel_siginfo), 0,
+ SI_EXPANSION_SIZE);
fill_note(note, "CORE", NT_SIGINFO, sizeof(*csigdata), csigdata);
}
--
2.25.1
