From: "Paweł Jasiak" <pawel@jasiak.xyz>
To: linux-kernel@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org, jack@suse.cz
Subject: PROBLEM: fanotify_mark EFAULT on x86
Date: Sun, 1 Nov 2020 22:27:38 +0100 [thread overview]
Message-ID: <20201101212738.GA16924@gmail.com> (raw)
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I am trying to run examples from man fanotify.7 but fanotify_mark always
fail with errno = EFAULT.
fanotify_mark declaration is
SYSCALL_DEFINE5(fanotify_mark, int, fanotify_fd, unsigned int, flags,
__u64, mask, int, dfd,
const char __user *, pathname)
When
fanotify_mark(4, FAN_MARK_ADD | FAN_MARK_ONLYDIR,
FAN_CREATE | FAN_ONDIR, AT_FDCWD, 0xdeadc0de)
is called on kernel side I can see in do_syscall_32_irqs_on that CPU
context is
bx = 0x4 = 4
cx = 0x9 = FAN_MARK_ADD | FAN_MARK_ONLYDIR,
dx = 0x40000100 = FAN_CREATE | FAN_ONDIR
si = 0x0
di = 0xffffff9c = AT_FDCWD
bp = 0xdeadc0de
ax = 0xffffffda
orix_ax = 0x153
I am not sure if it is ok because third argument is uint64_t so if I
understand correctly mask should be divided into two registers (dx and
si).
But in fanotify_mark we get
fanotify_fd = 4 = bx
flags = 0x9 = cx
mask = 0x40000100 = dx
dfd = 0 = si
pathname = 0xffffff9c = di
I believe that correct order is
fanotify_fd = 4 = bx
flags = 0x9 = cx
mask = 0x40000100 = (si << 32) | dx
dfd = 0xffffff9c = di
pathname = 0xdeadc0de = bp
I think that we should call COMPAT version of fanotify_mark here
COMPAT_SYSCALL_DEFINE6(fanotify_mark,
int, fanotify_fd, unsigned int, flags,
__u32, mask0, __u32, mask1, int, dfd,
const char __user *, pathname)
or something wrong is with 64-bits arguments.
I am running Linux 5.9.2 i686 on Pentium III (Coppermine).
For tests I am using Debian sid on qemu with 5.9.2 and default kernel
from repositories.
Everything works fine on 5.5 and 5.4.
--
Paweł Jasiak
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next reply other threads:[~2020-11-01 21:27 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-01 21:27 Paweł Jasiak [this message]
2020-11-01 21:38 ` PROBLEM: fanotify_mark EFAULT on x86 Matthew Wilcox
2020-11-01 22:27 ` Paweł Jasiak
2020-11-02 12:26 ` Jan Kara
2020-11-02 17:16 ` Paweł Jasiak
2020-11-03 21:17 ` Paweł Jasiak
2020-11-04 10:14 ` Jan Kara
2020-11-23 16:46 ` Jan Kara
2020-11-23 22:46 ` Paweł Jasiak
2020-11-24 8:45 ` Borislav Petkov
2020-11-24 10:20 ` Jan Kara
2020-11-24 10:28 ` Borislav Petkov
2020-11-26 10:48 ` Jan Kara
2020-11-26 10:52 ` Borislav Petkov
2020-11-25 19:31 ` Naresh Kamboju
2020-11-26 10:48 ` Jan Kara
2020-11-23 23:07 ` [PATCH] fanotify: Fix fanotify_mark() on 32-bit archs kernel test robot
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