Re: [PATCH] Avoid buffer overflows in get_user_pages()
Oliver Pinter <[EMAIL PROTECTED]> wrote: > for stable (.22 .23 .24) ? > > git id in mainline: 900cf086fd2fbad07f72f4575449e0d0958f860f I sent it to the stable folks a couple days ago. Thanks, jon Jonathan Corbet / LWN.net / [EMAIL PROTECTED] -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Avoid buffer overflows in get_user_pages()
for stable (.22 .23 .24) ?
git id in mainline: 900cf086fd2fbad07f72f4575449e0d0958f860f
--
tested in: http://repo.or.cz/w/linux-2.6.22.y-op.git testing
On 2/12/08, Jonathan Corbet <[EMAIL PROTECTED]> wrote:
> Avoid buffer overflows in get_user_pages()
>
> So I spent a while pounding my head against my monitor trying to figure
> out the vmsplice() vulnerability - how could a failure to check for
> *read* access turn into a root exploit? It turns out that it's a buffer
> overflow problem which is made easy by the way get_user_pages() is
> coded.
>
> In particular, "len" is a signed int, and it is only checked at the
> *end* of a do {} while() loop. So, if it is passed in as zero, the loop
> will execute once and decrement len to -1. At that point, the loop will
> proceed until the next invalid address is found; in the process, it will
> likely overflow the pages array passed in to get_user_pages().
>
> I think that, if get_user_pages() has been asked to grab zero pages,
> that's what it should do. Thus this patch; it is, among other things,
> enough to block the (already fixed) root exploit and any others which
> might be lurking in similar code. I also think that the number of pages
> should be unsigned, but changing the prototype of this function probably
> requires some more careful review.
>
> Signed-off-by: Jonathan Corbet <[EMAIL PROTECTED]>
>
> diff --git a/mm/memory.c b/mm/memory.c
> index e5628a5..7f50fd8 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -989,6 +989,8 @@ int get_user_pages(struct task_struct *tsk, struct
> mm_struct *mm,
> int i;
> unsigned int vm_flags;
>
> + if (len <= 0)
> + return 0;
> /*
> * Require read or write permissions.
> * If 'force' is set, we only require the "MAY" flags.
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [EMAIL PROTECTED]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
>
--
Thanks,
Oliver
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Re: [PATCH] Avoid buffer overflows in get_user_pages()
for stable (.22 .23 .24) ?
git id in mainline: 900cf086fd2fbad07f72f4575449e0d0958f860f
--
tested in: http://repo.or.cz/w/linux-2.6.22.y-op.git testing
On 2/12/08, Jonathan Corbet [EMAIL PROTECTED] wrote:
Avoid buffer overflows in get_user_pages()
So I spent a while pounding my head against my monitor trying to figure
out the vmsplice() vulnerability - how could a failure to check for
*read* access turn into a root exploit? It turns out that it's a buffer
overflow problem which is made easy by the way get_user_pages() is
coded.
In particular, len is a signed int, and it is only checked at the
*end* of a do {} while() loop. So, if it is passed in as zero, the loop
will execute once and decrement len to -1. At that point, the loop will
proceed until the next invalid address is found; in the process, it will
likely overflow the pages array passed in to get_user_pages().
I think that, if get_user_pages() has been asked to grab zero pages,
that's what it should do. Thus this patch; it is, among other things,
enough to block the (already fixed) root exploit and any others which
might be lurking in similar code. I also think that the number of pages
should be unsigned, but changing the prototype of this function probably
requires some more careful review.
Signed-off-by: Jonathan Corbet [EMAIL PROTECTED]
diff --git a/mm/memory.c b/mm/memory.c
index e5628a5..7f50fd8 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -989,6 +989,8 @@ int get_user_pages(struct task_struct *tsk, struct
mm_struct *mm,
int i;
unsigned int vm_flags;
+ if (len = 0)
+ return 0;
/*
* Require read or write permissions.
* If 'force' is set, we only require the MAY flags.
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--
Thanks,
Oliver
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Re: [PATCH] Avoid buffer overflows in get_user_pages()
Oliver Pinter [EMAIL PROTECTED] wrote: for stable (.22 .23 .24) ? git id in mainline: 900cf086fd2fbad07f72f4575449e0d0958f860f I sent it to the stable folks a couple days ago. Thanks, jon Jonathan Corbet / LWN.net / [EMAIL PROTECTED] -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Avoid buffer overflows in get_user_pages()
On Mon, 11 Feb 2008, Andrew Morton wrote:
> > + if (len <= 0)
> > + return 0;
> > /*
> > * Require read or write permissions.
> > * If 'force' is set, we only require the "MAY" flags.
> Can we just convert
> do {
> ...
> } while (len);
> into
> while (len) {
> ...
> }
How would that help?
Rather
while (len > 0) {
...
}
would do the trick.
--
Jiri Kosina
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Re: [PATCH] Avoid buffer overflows in get_user_pages()
Andrew Morton <[EMAIL PROTECTED]> wrote:
> On Mon, 11 Feb 2008 16:17:33 -0700 Jonathan Corbet <[EMAIL PROTECTED]> wrote:
>> Avoid buffer overflows in get_user_pages()
>>
>> So I spent a while pounding my head against my monitor trying to figure
>> out the vmsplice() vulnerability - how could a failure to check for
>> *read* access turn into a root exploit? It turns out that it's a buffer
>> overflow problem which is made easy by the way get_user_pages() is
>> coded.
>>
>> In particular, "len" is a signed int, and it is only checked at the
>> *end* of a do {} while() loop. So, if it is passed in as zero, the loop
>> will execute once and decrement len to -1. At that point, the loop will
>> proceed until the next invalid address is found; in the process, it will
>> likely overflow the pages array passed in to get_user_pages().
[...]
> Can we just convert
>
> do {
> ...
> } while (len);
>
> into
>
> while (len) {
while (len > 0), if I understand this patch correctly.
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Re: [PATCH] Avoid buffer overflows in get_user_pages()
Andrew Morton [EMAIL PROTECTED] wrote:
On Mon, 11 Feb 2008 16:17:33 -0700 Jonathan Corbet [EMAIL PROTECTED] wrote:
Avoid buffer overflows in get_user_pages()
So I spent a while pounding my head against my monitor trying to figure
out the vmsplice() vulnerability - how could a failure to check for
*read* access turn into a root exploit? It turns out that it's a buffer
overflow problem which is made easy by the way get_user_pages() is
coded.
In particular, len is a signed int, and it is only checked at the
*end* of a do {} while() loop. So, if it is passed in as zero, the loop
will execute once and decrement len to -1. At that point, the loop will
proceed until the next invalid address is found; in the process, it will
likely overflow the pages array passed in to get_user_pages().
[...]
Can we just convert
do {
...
} while (len);
into
while (len) {
while (len 0), if I understand this patch correctly.
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Re: [PATCH] Avoid buffer overflows in get_user_pages()
On Mon, 11 Feb 2008, Andrew Morton wrote:
+ if (len = 0)
+ return 0;
/*
* Require read or write permissions.
* If 'force' is set, we only require the MAY flags.
Can we just convert
do {
...
} while (len);
into
while (len) {
...
}
How would that help?
Rather
while (len 0) {
...
}
would do the trick.
--
Jiri Kosina
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Re: [PATCH] Avoid buffer overflows in get_user_pages()
On Mon, 11 Feb 2008 16:17:33 -0700 Jonathan Corbet <[EMAIL PROTECTED]> wrote:
> Avoid buffer overflows in get_user_pages()
>
> So I spent a while pounding my head against my monitor trying to figure
> out the vmsplice() vulnerability - how could a failure to check for
> *read* access turn into a root exploit? It turns out that it's a buffer
> overflow problem which is made easy by the way get_user_pages() is
> coded.
>
> In particular, "len" is a signed int, and it is only checked at the
> *end* of a do {} while() loop. So, if it is passed in as zero, the loop
> will execute once and decrement len to -1. At that point, the loop will
> proceed until the next invalid address is found; in the process, it will
> likely overflow the pages array passed in to get_user_pages().
Sounds convincing.
> I think that, if get_user_pages() has been asked to grab zero pages,
> that's what it should do. Thus this patch; it is, among other things,
> enough to block the (already fixed) root exploit and any others which
> might be lurking in similar code. I also think that the number of pages
> should be unsigned, but changing the prototype of this function probably
> requires some more careful review.
>
> Signed-off-by: Jonathan Corbet <[EMAIL PROTECTED]>
>
> diff --git a/mm/memory.c b/mm/memory.c
> index e5628a5..7f50fd8 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -989,6 +989,8 @@ int get_user_pages(struct task_struct *tsk, struct
> mm_struct *mm,
> int i;
> unsigned int vm_flags;
>
> + if (len <= 0)
> + return 0;
> /*
>* Require read or write permissions.
>* If 'force' is set, we only require the "MAY" flags.
Can we just convert
do {
...
} while (len);
into
while (len) {
...
}
?
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Re: [PATCH] Avoid buffer overflows in get_user_pages()
On Tuesday 12 February 2008 14:16, Robert Hancock wrote:
> Nick Piggin wrote:
> > On Tuesday 12 February 2008 10:17, Jonathan Corbet wrote:
> >> Avoid buffer overflows in get_user_pages()
> >>
> >> So I spent a while pounding my head against my monitor trying to figure
> >> out the vmsplice() vulnerability - how could a failure to check for
> >> *read* access turn into a root exploit? It turns out that it's a buffer
> >> overflow problem which is made easy by the way get_user_pages() is
> >> coded.
> >>
> >> In particular, "len" is a signed int, and it is only checked at the
> >> *end* of a do {} while() loop. So, if it is passed in as zero, the loop
> >> will execute once and decrement len to -1. At that point, the loop will
> >> proceed until the next invalid address is found; in the process, it will
> >> likely overflow the pages array passed in to get_user_pages().
> >>
> >> I think that, if get_user_pages() has been asked to grab zero pages,
> >> that's what it should do. Thus this patch; it is, among other things,
> >> enough to block the (already fixed) root exploit and any others which
> >> might be lurking in similar code. I also think that the number of pages
> >> should be unsigned, but changing the prototype of this function probably
> >> requires some more careful review.
> >>
> >> Signed-off-by: Jonathan Corbet <[EMAIL PROTECTED]>
> >>
> >> diff --git a/mm/memory.c b/mm/memory.c
> >> index e5628a5..7f50fd8 100644
> >> --- a/mm/memory.c
> >> +++ b/mm/memory.c
> >> @@ -989,6 +989,8 @@ int get_user_pages(struct task_struct *tsk, struct
> >> mm_struct *mm, int i;
> >>unsigned int vm_flags;
> >>
> >> + if (len <= 0)
> >> + return 0;
> >
> > BUG_ON()?
>
> Well, not if the code involved in the exploit can pass a zero value,
Which is a bug, and you want to catch it.
> otherwise it's just turning it into a DoS..
If it is due to a security bug, then the fix is to fix the point
where the kernel starts trusting an untrusted value. Not to hide
the bug like this. Arguably, a BUG_ON is better in the case of a
security hole because you want to halt the process as soon as you
detect a problem.
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Re: [PATCH] Avoid buffer overflows in get_user_pages()
Nick Piggin wrote:
On Tuesday 12 February 2008 10:17, Jonathan Corbet wrote:
Avoid buffer overflows in get_user_pages()
So I spent a while pounding my head against my monitor trying to figure
out the vmsplice() vulnerability - how could a failure to check for
*read* access turn into a root exploit? It turns out that it's a buffer
overflow problem which is made easy by the way get_user_pages() is
coded.
In particular, "len" is a signed int, and it is only checked at the
*end* of a do {} while() loop. So, if it is passed in as zero, the loop
will execute once and decrement len to -1. At that point, the loop will
proceed until the next invalid address is found; in the process, it will
likely overflow the pages array passed in to get_user_pages().
I think that, if get_user_pages() has been asked to grab zero pages,
that's what it should do. Thus this patch; it is, among other things,
enough to block the (already fixed) root exploit and any others which
might be lurking in similar code. I also think that the number of pages
should be unsigned, but changing the prototype of this function probably
requires some more careful review.
Signed-off-by: Jonathan Corbet <[EMAIL PROTECTED]>
diff --git a/mm/memory.c b/mm/memory.c
index e5628a5..7f50fd8 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -989,6 +989,8 @@ int get_user_pages(struct task_struct *tsk, struct
mm_struct *mm, int i;
unsigned int vm_flags;
+ if (len <= 0)
+ return 0;
BUG_ON()?
Well, not if the code involved in the exploit can pass a zero value,
otherwise it's just turning it into a DoS..
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Re: [PATCH] Avoid buffer overflows in get_user_pages()
On Tuesday 12 February 2008 10:17, Jonathan Corbet wrote:
> Avoid buffer overflows in get_user_pages()
>
> So I spent a while pounding my head against my monitor trying to figure
> out the vmsplice() vulnerability - how could a failure to check for
> *read* access turn into a root exploit? It turns out that it's a buffer
> overflow problem which is made easy by the way get_user_pages() is
> coded.
>
> In particular, "len" is a signed int, and it is only checked at the
> *end* of a do {} while() loop. So, if it is passed in as zero, the loop
> will execute once and decrement len to -1. At that point, the loop will
> proceed until the next invalid address is found; in the process, it will
> likely overflow the pages array passed in to get_user_pages().
>
> I think that, if get_user_pages() has been asked to grab zero pages,
> that's what it should do. Thus this patch; it is, among other things,
> enough to block the (already fixed) root exploit and any others which
> might be lurking in similar code. I also think that the number of pages
> should be unsigned, but changing the prototype of this function probably
> requires some more careful review.
>
> Signed-off-by: Jonathan Corbet <[EMAIL PROTECTED]>
>
> diff --git a/mm/memory.c b/mm/memory.c
> index e5628a5..7f50fd8 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -989,6 +989,8 @@ int get_user_pages(struct task_struct *tsk, struct
> mm_struct *mm, int i;
> unsigned int vm_flags;
>
> + if (len <= 0)
> + return 0;
BUG_ON()?
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[PATCH] Avoid buffer overflows in get_user_pages()
Avoid buffer overflows in get_user_pages()
So I spent a while pounding my head against my monitor trying to figure
out the vmsplice() vulnerability - how could a failure to check for
*read* access turn into a root exploit? It turns out that it's a buffer
overflow problem which is made easy by the way get_user_pages() is
coded.
In particular, "len" is a signed int, and it is only checked at the
*end* of a do {} while() loop. So, if it is passed in as zero, the loop
will execute once and decrement len to -1. At that point, the loop will
proceed until the next invalid address is found; in the process, it will
likely overflow the pages array passed in to get_user_pages().
I think that, if get_user_pages() has been asked to grab zero pages,
that's what it should do. Thus this patch; it is, among other things,
enough to block the (already fixed) root exploit and any others which
might be lurking in similar code. I also think that the number of pages
should be unsigned, but changing the prototype of this function probably
requires some more careful review.
Signed-off-by: Jonathan Corbet <[EMAIL PROTECTED]>
diff --git a/mm/memory.c b/mm/memory.c
index e5628a5..7f50fd8 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -989,6 +989,8 @@ int get_user_pages(struct task_struct *tsk, struct
mm_struct *mm,
int i;
unsigned int vm_flags;
+ if (len <= 0)
+ return 0;
/*
* Require read or write permissions.
* If 'force' is set, we only require the "MAY" flags.
--
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[PATCH] Avoid buffer overflows in get_user_pages()
Avoid buffer overflows in get_user_pages()
So I spent a while pounding my head against my monitor trying to figure
out the vmsplice() vulnerability - how could a failure to check for
*read* access turn into a root exploit? It turns out that it's a buffer
overflow problem which is made easy by the way get_user_pages() is
coded.
In particular, len is a signed int, and it is only checked at the
*end* of a do {} while() loop. So, if it is passed in as zero, the loop
will execute once and decrement len to -1. At that point, the loop will
proceed until the next invalid address is found; in the process, it will
likely overflow the pages array passed in to get_user_pages().
I think that, if get_user_pages() has been asked to grab zero pages,
that's what it should do. Thus this patch; it is, among other things,
enough to block the (already fixed) root exploit and any others which
might be lurking in similar code. I also think that the number of pages
should be unsigned, but changing the prototype of this function probably
requires some more careful review.
Signed-off-by: Jonathan Corbet [EMAIL PROTECTED]
diff --git a/mm/memory.c b/mm/memory.c
index e5628a5..7f50fd8 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -989,6 +989,8 @@ int get_user_pages(struct task_struct *tsk, struct
mm_struct *mm,
int i;
unsigned int vm_flags;
+ if (len = 0)
+ return 0;
/*
* Require read or write permissions.
* If 'force' is set, we only require the MAY flags.
--
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Re: [PATCH] Avoid buffer overflows in get_user_pages()
On Tuesday 12 February 2008 14:16, Robert Hancock wrote:
Nick Piggin wrote:
On Tuesday 12 February 2008 10:17, Jonathan Corbet wrote:
Avoid buffer overflows in get_user_pages()
So I spent a while pounding my head against my monitor trying to figure
out the vmsplice() vulnerability - how could a failure to check for
*read* access turn into a root exploit? It turns out that it's a buffer
overflow problem which is made easy by the way get_user_pages() is
coded.
In particular, len is a signed int, and it is only checked at the
*end* of a do {} while() loop. So, if it is passed in as zero, the loop
will execute once and decrement len to -1. At that point, the loop will
proceed until the next invalid address is found; in the process, it will
likely overflow the pages array passed in to get_user_pages().
I think that, if get_user_pages() has been asked to grab zero pages,
that's what it should do. Thus this patch; it is, among other things,
enough to block the (already fixed) root exploit and any others which
might be lurking in similar code. I also think that the number of pages
should be unsigned, but changing the prototype of this function probably
requires some more careful review.
Signed-off-by: Jonathan Corbet [EMAIL PROTECTED]
diff --git a/mm/memory.c b/mm/memory.c
index e5628a5..7f50fd8 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -989,6 +989,8 @@ int get_user_pages(struct task_struct *tsk, struct
mm_struct *mm, int i;
unsigned int vm_flags;
+ if (len = 0)
+ return 0;
BUG_ON()?
Well, not if the code involved in the exploit can pass a zero value,
Which is a bug, and you want to catch it.
otherwise it's just turning it into a DoS..
If it is due to a security bug, then the fix is to fix the point
where the kernel starts trusting an untrusted value. Not to hide
the bug like this. Arguably, a BUG_ON is better in the case of a
security hole because you want to halt the process as soon as you
detect a problem.
--
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the body of a message to [EMAIL PROTECTED]
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Re: [PATCH] Avoid buffer overflows in get_user_pages()
Nick Piggin wrote:
On Tuesday 12 February 2008 10:17, Jonathan Corbet wrote:
Avoid buffer overflows in get_user_pages()
So I spent a while pounding my head against my monitor trying to figure
out the vmsplice() vulnerability - how could a failure to check for
*read* access turn into a root exploit? It turns out that it's a buffer
overflow problem which is made easy by the way get_user_pages() is
coded.
In particular, len is a signed int, and it is only checked at the
*end* of a do {} while() loop. So, if it is passed in as zero, the loop
will execute once and decrement len to -1. At that point, the loop will
proceed until the next invalid address is found; in the process, it will
likely overflow the pages array passed in to get_user_pages().
I think that, if get_user_pages() has been asked to grab zero pages,
that's what it should do. Thus this patch; it is, among other things,
enough to block the (already fixed) root exploit and any others which
might be lurking in similar code. I also think that the number of pages
should be unsigned, but changing the prototype of this function probably
requires some more careful review.
Signed-off-by: Jonathan Corbet [EMAIL PROTECTED]
diff --git a/mm/memory.c b/mm/memory.c
index e5628a5..7f50fd8 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -989,6 +989,8 @@ int get_user_pages(struct task_struct *tsk, struct
mm_struct *mm, int i;
unsigned int vm_flags;
+ if (len = 0)
+ return 0;
BUG_ON()?
Well, not if the code involved in the exploit can pass a zero value,
otherwise it's just turning it into a DoS..
--
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Re: [PATCH] Avoid buffer overflows in get_user_pages()
On Tuesday 12 February 2008 10:17, Jonathan Corbet wrote:
Avoid buffer overflows in get_user_pages()
So I spent a while pounding my head against my monitor trying to figure
out the vmsplice() vulnerability - how could a failure to check for
*read* access turn into a root exploit? It turns out that it's a buffer
overflow problem which is made easy by the way get_user_pages() is
coded.
In particular, len is a signed int, and it is only checked at the
*end* of a do {} while() loop. So, if it is passed in as zero, the loop
will execute once and decrement len to -1. At that point, the loop will
proceed until the next invalid address is found; in the process, it will
likely overflow the pages array passed in to get_user_pages().
I think that, if get_user_pages() has been asked to grab zero pages,
that's what it should do. Thus this patch; it is, among other things,
enough to block the (already fixed) root exploit and any others which
might be lurking in similar code. I also think that the number of pages
should be unsigned, but changing the prototype of this function probably
requires some more careful review.
Signed-off-by: Jonathan Corbet [EMAIL PROTECTED]
diff --git a/mm/memory.c b/mm/memory.c
index e5628a5..7f50fd8 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -989,6 +989,8 @@ int get_user_pages(struct task_struct *tsk, struct
mm_struct *mm, int i;
unsigned int vm_flags;
+ if (len = 0)
+ return 0;
BUG_ON()?
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Re: [PATCH] Avoid buffer overflows in get_user_pages()
On Mon, 11 Feb 2008 16:17:33 -0700 Jonathan Corbet [EMAIL PROTECTED] wrote:
Avoid buffer overflows in get_user_pages()
So I spent a while pounding my head against my monitor trying to figure
out the vmsplice() vulnerability - how could a failure to check for
*read* access turn into a root exploit? It turns out that it's a buffer
overflow problem which is made easy by the way get_user_pages() is
coded.
In particular, len is a signed int, and it is only checked at the
*end* of a do {} while() loop. So, if it is passed in as zero, the loop
will execute once and decrement len to -1. At that point, the loop will
proceed until the next invalid address is found; in the process, it will
likely overflow the pages array passed in to get_user_pages().
Sounds convincing.
I think that, if get_user_pages() has been asked to grab zero pages,
that's what it should do. Thus this patch; it is, among other things,
enough to block the (already fixed) root exploit and any others which
might be lurking in similar code. I also think that the number of pages
should be unsigned, but changing the prototype of this function probably
requires some more careful review.
Signed-off-by: Jonathan Corbet [EMAIL PROTECTED]
diff --git a/mm/memory.c b/mm/memory.c
index e5628a5..7f50fd8 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -989,6 +989,8 @@ int get_user_pages(struct task_struct *tsk, struct
mm_struct *mm,
int i;
unsigned int vm_flags;
+ if (len = 0)
+ return 0;
/*
* Require read or write permissions.
* If 'force' is set, we only require the MAY flags.
Can we just convert
do {
...
} while (len);
into
while (len) {
...
}
?
--
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