As sparse points out, these two copy_from_user() should actually be
copy_to_user().
Fixes: 229b53c9bf4e ("take floppy compat ioctls to sodding floppy.c")
Cc: [email protected]
Signed-off-by: Jann Horn <[email protected]>
---
compile-tested only
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:
--
2.21.0.392.gf8f6787159e-goog
On 3/27/2019 3:33 AM, Jann Horn wrote:
> As sparse points out, these two copy_from_user() should actually be
> copy_to_user().
>
> Fixes: 229b53c9bf4e ("take floppy compat ioctls to sodding floppy.c")
> Cc: [email protected]
> Signed-off-by: Jann Horn <[email protected]>
Reviewed-by: Mukesh Ojha <[email protected]>
> ---
> compile-tested only
>
> 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:
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: [email protected]
> Signed-off-by: Jann Horn <[email protected]>
> Reviewed-by: Mukesh Ojha <[email protected]>
> ---
> compile-tested only
Acked-by: Alexander Popov <[email protected]>
> 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
On 8/9/19 6:36 AM, Alexander Popov wrote:
> 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.
Looks like it got lost indeed, I will just apply this one directly for
5.4.
--
Jens Axboe
>> So I add a new floppy maintainer Denis Efremov to CC.
>
> Looks like it got lost indeed, I will just apply this one directly for
> 5.4.
>
Thank you!
Denis
On Fri, 9 Aug 2019, Alexander Popov wrote:
> 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: [email protected]
> > Signed-off-by: Jann Horn <[email protected]>
> > Reviewed-by: Mukesh Ojha <[email protected]>
> > ---
> > compile-tested only
>
> Acked-by: Alexander Popov <[email protected]>
>
> > 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@
You can replace the above line with @cfu exists@. You want to find the
existence of such a call, not ensure that the call occurs on every
control-flow path, which is the default.
Do you want this rule to go into the kernel?
julia
> 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
>
On 09.08.2019 16:56, Julia Lawall wrote:
> On Fri, 9 Aug 2019, Alexander Popov wrote:
>> 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 also wrote a coccinelle rule for detecting similar bugs (adding coccinelle
>> experts to CC).
>>
>>
>> virtual report
>>
>> @cfu@
>
> You can replace the above line with @cfu exists@. You want to find the
> existence of such a call, not ensure that the call occurs on every
> control-flow path, which is the default.
Thanks Julia, I see `exists` allows to drop `<+ +>`, right?
> Do you want this rule to go into the kernel?
It turned out that sparse already can find these bugs.
Is this rule useful anyway? If so, I can prepare a patch.
>> 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!
> …, I see `exists` allows to drop `<+ +>`, right?
I would interpret the combination of such SmPL specifications in a different way.
> It turned out that sparse already can find these bugs.
This is generally nice, isn't it?
> Is this rule useful anyway?
I hope so.
Can scripts for the semantic patch language help any more?
> If so, I can prepare a patch.
Would you like to take corresponding adjustments into account?
Regards,
Markus
On Fri, 9 Aug 2019, Alexander Popov wrote:
> On 09.08.2019 16:56, Julia Lawall wrote:
> > On Fri, 9 Aug 2019, Alexander Popov wrote:
> >> 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 also wrote a coccinelle rule for detecting similar bugs (adding coccinelle
> >> experts to CC).
> >>
> >>
> >> virtual report
> >>
> >> @cfu@
> >
> > You can replace the above line with @cfu exists@. You want to find the
> > existence of such a call, not ensure that the call occurs on every
> > control-flow path, which is the default.
>
> Thanks Julia, I see `exists` allows to drop `<+ +>`, right?
Exists is more efficient when it is possible. It just finds the existence
of a path that has the property rather than collecting information about
all paths. It is related to <+... ...+> because for that there has to
exist at least one match. You could probably do something like
... when any
copy_from_user
... when any
Then with exists you will consider each call one at a time.
>
> > Do you want this rule to go into the kernel?
>
> It turned out that sparse already can find these bugs.
If sparse is already doing this, then perhaps that's sufficient. Someone
just has to be running it :)
julia
> Is this rule useful anyway? If so, I can prepare a patch.
>
> >> 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!
>
> @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:
Can this check be specified as a constraint for a metavariable
in the initial SmPL rule?
Would you like to move it to an other place?
Regards,
Markus