From: Alexander Popov <alex.popov@linux.com> To: Jann Horn <jannh@google.com>, Jens Axboe <axboe@kernel.dk> Cc: Jiri Kosina <jikos@kernel.org>, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Al Viro <viro@zeniv.linux.org.uk>, Mukesh Ojha <mojha@codeaurora.org>, "kernel-hardening@lists.openwall.com" <kernel-hardening@lists.openwall.com>, Denis Efremov <efremov@linux.com>, Julia Lawall <Julia.Lawall@lip6.fr>, Gilles Muller <Gilles.Muller@lip6.fr>, Nicolas Palix <nicolas.palix@imag.fr>, Michal Marek <michal.lkml@markovi.net>, cocci@systeme.lip6.fr Subject: Re: [PATCH] floppy: fix usercopy direction Date: Fri, 9 Aug 2019 16:36:52 +0300 [thread overview] Message-ID: <9ced7a06-5048-ad1a-3428-c8f943f7469c@linux.com> (raw) In-Reply-To: <20190326220348.61172-1-jannh@google.com> Hello everyone! On 27.03.2019 1:03, Jann Horn wrote: > As sparse points out, these two copy_from_user() should actually be > copy_to_user(). I've spent some time on these bugs, but it turned out that they are already public. I think Jann's patch is lost, it is not applied to the mainline. So I add a new floppy maintainer Denis Efremov to CC. These bugs on x86_64 cause memset for the userspace memory from the kernelspace. That is funny: - access_ok for the copy_from_user source (2nd argument) returns zero; - copy_from_user tries to erase the destination (1st argument); - but the destination is in the userspace instead of kernelspace. So we have: [ 40.937098] BUG: unable to handle page fault for address: 0000000041414242 [ 40.938714] #PF: supervisor write access in kernel mode [ 40.939951] #PF: error_code(0x0002) - not-present page [ 40.941121] PGD 7963f067 P4D 7963f067 PUD 0 [ 40.942107] Oops: 0002 [#1] SMP NOPTI [ 40.942968] CPU: 0 PID: 292 Comm: d Not tainted 5.3.0-rc3+ #7 [ 40.944288] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 [ 40.946478] RIP: 0010:__memset+0x24/0x30 [ 40.947394] Code: 90 90 90 90 90 90 0f 1f 44 00 00 49 89 f9 48 89 d1 83 e2 07 48 c1 e9 03 40 0f b6 f6 48 b8 01 01 01 01 01 01 01 01 48 0f af c6 <f3> 48 ab 89 d1 f3 aa 4c 89 c8 c3 90 49 89 f9 40 88 f0 48 89 d1 f3 [ 40.951721] RSP: 0018:ffffc900003dbd58 EFLAGS: 00010206 [ 40.952941] RAX: 0000000000000000 RBX: 0000000000000034 RCX: 0000000000000006 [ 40.954592] RDX: 0000000000000004 RSI: 0000000000000000 RDI: 0000000041414242 [ 40.956169] RBP: 0000000041414242 R08: ffffffff8200bd80 R09: 0000000041414242 [ 40.957753] R10: 0000000000121806 R11: ffff88807da28ab0 R12: ffffc900003dbd7c [ 40.959407] R13: 0000000000000001 R14: 0000000041414242 R15: 0000000041414242 [ 40.961062] FS: 00007f91115c4440(0000) GS:ffff88807da00000(0000) knlGS:0000000000000000 [ 40.962603] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 40.963695] CR2: 0000000041414242 CR3: 000000007c584000 CR4: 00000000000006f0 [ 40.965004] Call Trace: [ 40.965459] _copy_from_user+0x51/0x60 [ 40.966141] compat_getdrvstat+0x124/0x170 [ 40.966781] fd_compat_ioctl+0x69c/0x6d0 [ 40.967423] ? selinux_file_ioctl+0x16f/0x210 [ 40.968117] compat_blkdev_ioctl+0x21d/0x8f0 [ 40.968864] __x32_compat_sys_ioctl+0x99/0x250 [ 40.969659] do_syscall_64+0x4a/0x110 [ 40.970337] entry_SYSCALL_64_after_hwframe+0x44/0xa9 I haven't found a way to exploit it. > Fixes: 229b53c9bf4e ("take floppy compat ioctls to sodding floppy.c") > Cc: stable@vger.kernel.org > Signed-off-by: Jann Horn <jannh@google.com> > Reviewed-by: Mukesh Ojha <mojha@codeaurora.org> > --- > compile-tested only Acked-by: Alexander Popov <alex.popov@linux.com> > drivers/block/floppy.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c > index 95f608d1a098..8c641245ff12 100644 > --- a/drivers/block/floppy.c > +++ b/drivers/block/floppy.c > @@ -3749,7 +3749,7 @@ static int compat_getdrvprm(int drive, > v.native_format = UDP->native_format; > mutex_unlock(&floppy_mutex); > > - if (copy_from_user(arg, &v, sizeof(struct compat_floppy_drive_params))) > + if (copy_to_user(arg, &v, sizeof(struct compat_floppy_drive_params))) > return -EFAULT; > return 0; > } > @@ -3785,7 +3785,7 @@ static int compat_getdrvstat(int drive, bool poll, > v.bufblocks = UDRS->bufblocks; > mutex_unlock(&floppy_mutex); > > - if (copy_from_user(arg, &v, sizeof(struct compat_floppy_drive_struct))) > + if (copy_to_user(arg, &v, sizeof(struct compat_floppy_drive_struct))) > return -EFAULT; > return 0; > Eintr: > I also wrote a coccinelle rule for detecting similar bugs (adding coccinelle experts to CC). virtual report @cfu@ identifier f; type t; identifier v; position decl_p; position copy_p; @@ f(..., t v@decl_p, ...) { <+... copy_from_user@copy_p(v, ...) ...+> } @script:python@ f << cfu.f; t << cfu.t; v << cfu.v; decl_p << cfu.decl_p; copy_p << cfu.copy_p; @@ if '__user' in t: msg0 = "function \"" + f + "\" has arg \"" + v + "\" of type \"" + t + "\"" coccilib.report.print_report(decl_p[0], msg0) msg1 = "copy_from_user uses \"" + v + "\" as the destination. What a shame!\n" coccilib.report.print_report(copy_p[0], msg1) The rule output: ./drivers/block/floppy.c:3756:49-52: function "compat_getdrvprm" has arg "arg" of type "struct compat_floppy_drive_params __user *" ./drivers/block/floppy.c:3783:5-19: copy_from_user uses "arg" as the destination. What a shame! ./drivers/block/floppy.c:3789:49-52: function "compat_getdrvstat" has arg "arg" of type "struct compat_floppy_drive_struct __user *" ./drivers/block/floppy.c:3819:5-19: copy_from_user uses "arg" as the destination. What a shame! Best regards, Alexander
WARNING: multiple messages have this Message-ID (diff)
From: Alexander Popov <alex.popov@linux.com> To: Jann Horn <jannh@google.com>, Jens Axboe <axboe@kernel.dk> Cc: Michal Marek <michal.lkml@markovi.net>, "kernel-hardening@lists.openwall.com" <kernel-hardening@lists.openwall.com>, Mukesh Ojha <mojha@codeaurora.org>, Jiri Kosina <jikos@kernel.org>, Nicolas Palix <nicolas.palix@imag.fr>, linux-kernel@vger.kernel.org, Denis Efremov <efremov@linux.com>, linux-block@vger.kernel.org, Al Viro <viro@zeniv.linux.org.uk>, cocci@systeme.lip6.fr Subject: Re: [Cocci] [PATCH] floppy: fix usercopy direction Date: Fri, 9 Aug 2019 16:36:52 +0300 [thread overview] Message-ID: <9ced7a06-5048-ad1a-3428-c8f943f7469c@linux.com> (raw) In-Reply-To: <20190326220348.61172-1-jannh@google.com> Hello everyone! On 27.03.2019 1:03, Jann Horn wrote: > As sparse points out, these two copy_from_user() should actually be > copy_to_user(). I've spent some time on these bugs, but it turned out that they are already public. I think Jann's patch is lost, it is not applied to the mainline. So I add a new floppy maintainer Denis Efremov to CC. These bugs on x86_64 cause memset for the userspace memory from the kernelspace. That is funny: - access_ok for the copy_from_user source (2nd argument) returns zero; - copy_from_user tries to erase the destination (1st argument); - but the destination is in the userspace instead of kernelspace. So we have: [ 40.937098] BUG: unable to handle page fault for address: 0000000041414242 [ 40.938714] #PF: supervisor write access in kernel mode [ 40.939951] #PF: error_code(0x0002) - not-present page [ 40.941121] PGD 7963f067 P4D 7963f067 PUD 0 [ 40.942107] Oops: 0002 [#1] SMP NOPTI [ 40.942968] CPU: 0 PID: 292 Comm: d Not tainted 5.3.0-rc3+ #7 [ 40.944288] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 [ 40.946478] RIP: 0010:__memset+0x24/0x30 [ 40.947394] Code: 90 90 90 90 90 90 0f 1f 44 00 00 49 89 f9 48 89 d1 83 e2 07 48 c1 e9 03 40 0f b6 f6 48 b8 01 01 01 01 01 01 01 01 48 0f af c6 <f3> 48 ab 89 d1 f3 aa 4c 89 c8 c3 90 49 89 f9 40 88 f0 48 89 d1 f3 [ 40.951721] RSP: 0018:ffffc900003dbd58 EFLAGS: 00010206 [ 40.952941] RAX: 0000000000000000 RBX: 0000000000000034 RCX: 0000000000000006 [ 40.954592] RDX: 0000000000000004 RSI: 0000000000000000 RDI: 0000000041414242 [ 40.956169] RBP: 0000000041414242 R08: ffffffff8200bd80 R09: 0000000041414242 [ 40.957753] R10: 0000000000121806 R11: ffff88807da28ab0 R12: ffffc900003dbd7c [ 40.959407] R13: 0000000000000001 R14: 0000000041414242 R15: 0000000041414242 [ 40.961062] FS: 00007f91115c4440(0000) GS:ffff88807da00000(0000) knlGS:0000000000000000 [ 40.962603] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 40.963695] CR2: 0000000041414242 CR3: 000000007c584000 CR4: 00000000000006f0 [ 40.965004] Call Trace: [ 40.965459] _copy_from_user+0x51/0x60 [ 40.966141] compat_getdrvstat+0x124/0x170 [ 40.966781] fd_compat_ioctl+0x69c/0x6d0 [ 40.967423] ? selinux_file_ioctl+0x16f/0x210 [ 40.968117] compat_blkdev_ioctl+0x21d/0x8f0 [ 40.968864] __x32_compat_sys_ioctl+0x99/0x250 [ 40.969659] do_syscall_64+0x4a/0x110 [ 40.970337] entry_SYSCALL_64_after_hwframe+0x44/0xa9 I haven't found a way to exploit it. > Fixes: 229b53c9bf4e ("take floppy compat ioctls to sodding floppy.c") > Cc: stable@vger.kernel.org > Signed-off-by: Jann Horn <jannh@google.com> > Reviewed-by: Mukesh Ojha <mojha@codeaurora.org> > --- > compile-tested only Acked-by: Alexander Popov <alex.popov@linux.com> > drivers/block/floppy.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c > index 95f608d1a098..8c641245ff12 100644 > --- a/drivers/block/floppy.c > +++ b/drivers/block/floppy.c > @@ -3749,7 +3749,7 @@ static int compat_getdrvprm(int drive, > v.native_format = UDP->native_format; > mutex_unlock(&floppy_mutex); > > - if (copy_from_user(arg, &v, sizeof(struct compat_floppy_drive_params))) > + if (copy_to_user(arg, &v, sizeof(struct compat_floppy_drive_params))) > return -EFAULT; > return 0; > } > @@ -3785,7 +3785,7 @@ static int compat_getdrvstat(int drive, bool poll, > v.bufblocks = UDRS->bufblocks; > mutex_unlock(&floppy_mutex); > > - if (copy_from_user(arg, &v, sizeof(struct compat_floppy_drive_struct))) > + if (copy_to_user(arg, &v, sizeof(struct compat_floppy_drive_struct))) > return -EFAULT; > return 0; > Eintr: > I also wrote a coccinelle rule for detecting similar bugs (adding coccinelle experts to CC). virtual report @cfu@ identifier f; type t; identifier v; position decl_p; position copy_p; @@ f(..., t v@decl_p, ...) { <+... copy_from_user@copy_p(v, ...) ...+> } @script:python@ f << cfu.f; t << cfu.t; v << cfu.v; decl_p << cfu.decl_p; copy_p << cfu.copy_p; @@ if '__user' in t: msg0 = "function \"" + f + "\" has arg \"" + v + "\" of type \"" + t + "\"" coccilib.report.print_report(decl_p[0], msg0) msg1 = "copy_from_user uses \"" + v + "\" as the destination. What a shame!\n" coccilib.report.print_report(copy_p[0], msg1) The rule output: ./drivers/block/floppy.c:3756:49-52: function "compat_getdrvprm" has arg "arg" of type "struct compat_floppy_drive_params __user *" ./drivers/block/floppy.c:3783:5-19: copy_from_user uses "arg" as the destination. What a shame! ./drivers/block/floppy.c:3789:49-52: function "compat_getdrvstat" has arg "arg" of type "struct compat_floppy_drive_struct __user *" ./drivers/block/floppy.c:3819:5-19: copy_from_user uses "arg" as the destination. What a shame! Best regards, Alexander _______________________________________________ Cocci mailing list Cocci@systeme.lip6.fr https://systeme.lip6.fr/mailman/listinfo/cocci
next prev parent reply other threads:[~2019-08-09 13:36 UTC|newest] Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-03-26 22:03 [PATCH] floppy: fix usercopy direction Jann Horn 2019-03-27 12:02 ` Mukesh Ojha 2019-08-09 13:36 ` Alexander Popov [this message] 2019-08-09 13:36 ` Alexander Popov 2019-08-09 13:36 ` [Cocci] " Alexander Popov 2019-08-09 13:41 ` Jens Axboe 2019-08-09 13:41 ` Jens Axboe 2019-08-09 13:41 ` [Cocci] " Jens Axboe 2019-08-09 13:43 ` Denis Efremov 2019-08-09 13:43 ` Denis Efremov 2019-08-09 13:43 ` [Cocci] " Denis Efremov 2019-08-09 13:56 ` Julia Lawall 2019-08-09 13:56 ` Julia Lawall 2019-08-09 13:56 ` [Cocci] " Julia Lawall 2019-08-09 15:05 ` Alexander Popov 2019-08-09 15:05 ` Alexander Popov 2019-08-09 15:05 ` [Cocci] " Alexander Popov 2019-08-12 10:00 ` Markus Elfring 2019-08-12 10:00 ` [Cocci] " Markus Elfring 2019-08-12 10:00 ` Markus Elfring 2019-08-12 10:25 ` [PATCH] " Julia Lawall 2019-08-12 10:25 ` Julia Lawall 2019-08-12 10:25 ` [Cocci] " Julia Lawall 2019-08-13 7:50 ` Markus Elfring 2019-08-13 7:50 ` [Cocci] " Markus Elfring
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