On Tue, Mar 06, 2018 at 01:11:03AM -0600, Eric W. Biederman wrote:
Linus,
Please pull the siginfo-linus branch from the git tree:
git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git siginfo-linus
HEAD: f6a015498dcaee72f80283cb7873d88deb07129c signal/x86: Include the field offsets in the build time checks
The kbuild test robot found that I accidentally moved si_pkey when I was
cleaning up siginfo_t. A short followed by an int with the int having 8
byte alignment. Sheesh siginfo_t is a weird structure.
I have now corrected it and added build time checks that with a little
luck will catch any similar future mistakes. The build time checks were
sufficient for me to verify the bug and to verify my fix. So they are
at least useful this once.
Eric W. Biederman (2):
signal: Correct the offset of si_pkey in struct siginfo
Looks like this commit changes layout of the siginfo struct on m68k:
pts/0, esyr@fedora: /tmp % cat si.c
#include <stddef.h>
#include "linux/signal.h"
static const size_t lower_offset = offsetof(struct siginfo, si_lower);
pts/0, esyr@fedora: /tmp % m68k-linux-gnu-gcc -Ikhdr-v4.16-rc1\~159\^2\~20/include -g -c si.c -o si-orig.o
pts/0, esyr@fedora: /tmp % m68k-linux-gnu-gcc -Ikhdr-v4.16-rc3\~17\^2/include -g -c si.c -o si-1.o
pts/0, esyr@fedora: /tmp % m68k-linux-gnu-gcc -Ikhdr-v4.16-rc7-194-g29d9d38/include -g -c si.c -o si-2.o
pts/0, esyr@fedora: /tmp % for i in si-orig.o si-1.o si-2.o; do echo -------- $i; objdump -t -j .rodata $i; objdump -s -j .rodata $i; done
-------- si-orig.o
si-orig.o: file format elf32-big
SYMBOL TABLE:
00000000 l d .rodata 00000000 .rodata
00000000 l O .rodata 00000004 lower_offset
si-orig.o: file format elf32-big
Contents of section .rodata:
0000 00000012 ....
-------- si-1.o
si-1.o: file format elf32-big
SYMBOL TABLE:
00000000 l d .rodata 00000000 .rodata
00000000 l O .rodata 00000004 lower_offset
si-1.o: file format elf32-big
Contents of section .rodata:
0000 00000012 ....
-------- si-2.o
si-2.o: file format elf32-big
SYMBOL TABLE:
00000000 l d .rodata 00000000 .rodata
00000000 l O .rodata 00000004 lower_offset
si-2.o: file format elf32-big
Contents of section .rodata:
0000 00000014 ....
So, the offset of the si_lower field is 20 at the current HEAD and was 18 at
commits v4.16-rc3~17^2 and v4.16-rc1~159^2~20. I believe this is due to
the fact that m68k uses 2-byte default alignment and not 4-byte.
signal/x86: Include the field offsets in the build time checks
arch/x86/kernel/signal_compat.c | 65 ++++++++++++++++++++++++++++++++++++++
include/linux/compat.h | 4 +--
include/uapi/asm-generic/siginfo.h | 4 +--
3 files changed, 69 insertions(+), 4 deletions(-)
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