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[PATCH V3] bcachefs: Add journal v2 entry nr value check

Lizhi Xu posted 1 patch 1 year, 5 months ago 
fs/bcachefs/journal_sb.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
[PATCH V3] bcachefs: Add journal v2 entry nr value check
Posted by Lizhi Xu 1 year, 5 months ago 
When the nr value of a signle entry or their sum overflows, it will
cause the value of ja->nr to be incorrect, this will result in the
allocated memory to ja->buckets being too small, leading to out of
bounds access in bch2_dev_journal_init.

Reported-by: syzbot+47ecc948aadfb2ab3efc@syzkaller.appspotmail.com
Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
---
 fs/bcachefs/journal_sb.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/fs/bcachefs/journal_sb.c b/fs/bcachefs/journal_sb.c
index db80e506e3ab..230ed99130e4 100644
--- a/fs/bcachefs/journal_sb.c
+++ b/fs/bcachefs/journal_sb.c
@@ -107,6 +107,7 @@ static int bch2_sb_journal_v2_validate(struct bch_sb *sb, struct bch_sb_field *f
 	unsigned nr;
 	unsigned i;
 	struct u64_range *b;
+	u64 total_nr = 0, entry_nr;
 
 	nr = bch2_sb_field_journal_v2_nr_entries(journal);
 	if (!nr)
@@ -117,8 +118,21 @@ static int bch2_sb_journal_v2_validate(struct bch_sb *sb, struct bch_sb_field *f
 		return -BCH_ERR_ENOMEM_sb_journal_v2_validate;
 
 	for (i = 0; i < nr; i++) {
+		entry_nr = le64_to_cpu(journal->d[i].nr);
+		if (entry_nr > UINT_MAX) {
+			prt_printf(err, "Journal v2 entry d[%u] nr %llu overflow\n",
+				i, entry_nr);
+			goto err;
+		}
+		total_nr += entry_nr;
 		b[i].start = le64_to_cpu(journal->d[i].start);
-		b[i].end = b[i].start + le64_to_cpu(journal->d[i].nr);
+		b[i].end = b[i].start + entry_nr;
+	}
+
+	if (total_nr > UINT_MAX) {
+		prt_printf(err, "Sum of journal v2 entries nr %llu overflow\n",
+				total_nr);
+		goto err;
 	}
 
 	sort(b, nr, sizeof(*b), u64_range_cmp, NULL);
-- 
2.43.0
Re: [PATCH V3] bcachefs: Add journal v2 entry nr value check
Posted by Kent Overstreet 1 year, 5 months ago 
On Wed, Aug 21, 2024 at 10:57:37AM GMT, Lizhi Xu wrote:
> When the nr value of a signle entry or their sum overflows, it will
> cause the value of ja->nr to be incorrect, this will result in the
> allocated memory to ja->buckets being too small, leading to out of
> bounds access in bch2_dev_journal_init.
> 
> Reported-by: syzbot+47ecc948aadfb2ab3efc@syzkaller.appspotmail.com
> Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
> ---
>  fs/bcachefs/journal_sb.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/bcachefs/journal_sb.c b/fs/bcachefs/journal_sb.c
> index db80e506e3ab..230ed99130e4 100644
> --- a/fs/bcachefs/journal_sb.c
> +++ b/fs/bcachefs/journal_sb.c
> @@ -107,6 +107,7 @@ static int bch2_sb_journal_v2_validate(struct bch_sb *sb, struct bch_sb_field *f
>  	unsigned nr;
>  	unsigned i;
>  	struct u64_range *b;
> +	u64 total_nr = 0, entry_nr;
>  
>  	nr = bch2_sb_field_journal_v2_nr_entries(journal);
>  	if (!nr)
> @@ -117,8 +118,21 @@ static int bch2_sb_journal_v2_validate(struct bch_sb *sb, struct bch_sb_field *f
>  		return -BCH_ERR_ENOMEM_sb_journal_v2_validate;
>  
>  	for (i = 0; i < nr; i++) {
> +		entry_nr = le64_to_cpu(journal->d[i].nr);
> +		if (entry_nr > UINT_MAX) {
> +			prt_printf(err, "Journal v2 entry d[%u] nr %llu overflow\n",
> +				i, entry_nr);
> +			goto err;
> +		}

This check is unnecessary; we know the sum can't overflow a u64 because
we're also checking that the entries are nonoverlapping.

> +		total_nr += entry_nr;
>  		b[i].start = le64_to_cpu(journal->d[i].start);
> -		b[i].end = b[i].start + le64_to_cpu(journal->d[i].nr);
> +		b[i].end = b[i].start + entry_nr;
> +	}
> +
> +	if (total_nr > UINT_MAX) {
> +		prt_printf(err, "Sum of journal v2 entries nr %llu overflow\n",
> +				total_nr);
> +		goto err;
>  	}
>  
>  	sort(b, nr, sizeof(*b), u64_range_cmp, NULL);
> -- 
> 2.43.0
>
Re: [PATCH V3] bcachefs: Add journal v2 entry nr value check
Posted by Lizhi Xu 1 year, 5 months ago 
On Tue, 20 Aug 2024 23:00:05 -0400, Kent Overstreet wrote:
> > When the nr value of a signle entry or their sum overflows, it will
> > cause the value of ja->nr to be incorrect, this will result in the
> > allocated memory to ja->buckets being too small, leading to out of
> > bounds access in bch2_dev_journal_init.
> > 
> > Reported-by: syzbot+47ecc948aadfb2ab3efc@syzkaller.appspotmail.com
> > Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
> > ---
> >  fs/bcachefs/journal_sb.c | 16 +++++++++++++++-
> >  1 file changed, 15 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/bcachefs/journal_sb.c b/fs/bcachefs/journal_sb.c
> > index db80e506e3ab..230ed99130e4 100644
> > --- a/fs/bcachefs/journal_sb.c
> > +++ b/fs/bcachefs/journal_sb.c
> > @@ -107,6 +107,7 @@ static int bch2_sb_journal_v2_validate(struct bch_sb *sb, struct bch_sb_field *f
> >  	unsigned nr;
> >  	unsigned i;
> >  	struct u64_range *b;
> > +	u64 total_nr = 0, entry_nr;
> >  
> >  	nr = bch2_sb_field_journal_v2_nr_entries(journal);
> >  	if (!nr)
> > @@ -117,8 +118,21 @@ static int bch2_sb_journal_v2_validate(struct bch_sb *sb, struct bch_sb_field *f
> >  		return -BCH_ERR_ENOMEM_sb_journal_v2_validate;
> >  
> >  	for (i = 0; i < nr; i++) {
> > +		entry_nr = le64_to_cpu(journal->d[i].nr);
> > +		if (entry_nr > UINT_MAX) {
> > +			prt_printf(err, "Journal v2 entry d[%u] nr %llu overflow\n",
> > +				i, entry_nr);
> > +			goto err;
> > +		}
> 
> This check is unnecessary; we know the sum can't overflow a u64 because
> we're also checking that the entries are nonoverlapping.
You didn't read my previous email carefully.
In this issue, journal->d[0] is 7, journal->d[1] is 18446744073709551615,
so the sum of their u64 type values will definitely overflow.
> 
> > +		total_nr += entry_nr;
> >  		b[i].start = le64_to_cpu(journal->d[i].start);
> > -		b[i].end = b[i].start + le64_to_cpu(journal->d[i].nr);
> > +		b[i].end = b[i].start + entry_nr;
> > +	}
> > +
> > +	if (total_nr > UINT_MAX) {
> > +		prt_printf(err, "Sum of journal v2 entries nr %llu overflow\n",
> > +				total_nr);
> > +		goto err;
> >  	}
> >  
> >  	sort(b, nr, sizeof(*b), u64_range_cmp, NULL);
> > -- 

BR,
Lizhi
Re: [PATCH V3] bcachefs: Add journal v2 entry nr value check
Posted by Kent Overstreet 1 year, 5 months ago 
On Wed, Aug 21, 2024 at 11:10:00AM GMT, Lizhi Xu wrote:
> On Tue, 20 Aug 2024 23:00:05 -0400, Kent Overstreet wrote:
> > > When the nr value of a signle entry or their sum overflows, it will
> > > cause the value of ja->nr to be incorrect, this will result in the
> > > allocated memory to ja->buckets being too small, leading to out of
> > > bounds access in bch2_dev_journal_init.
> > > 
> > > Reported-by: syzbot+47ecc948aadfb2ab3efc@syzkaller.appspotmail.com
> > > Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
> > > ---
> > >  fs/bcachefs/journal_sb.c | 16 +++++++++++++++-
> > >  1 file changed, 15 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/fs/bcachefs/journal_sb.c b/fs/bcachefs/journal_sb.c
> > > index db80e506e3ab..230ed99130e4 100644
> > > --- a/fs/bcachefs/journal_sb.c
> > > +++ b/fs/bcachefs/journal_sb.c
> > > @@ -107,6 +107,7 @@ static int bch2_sb_journal_v2_validate(struct bch_sb *sb, struct bch_sb_field *f
> > >  	unsigned nr;
> > >  	unsigned i;
> > >  	struct u64_range *b;
> > > +	u64 total_nr = 0, entry_nr;
> > >  
> > >  	nr = bch2_sb_field_journal_v2_nr_entries(journal);
> > >  	if (!nr)
> > > @@ -117,8 +118,21 @@ static int bch2_sb_journal_v2_validate(struct bch_sb *sb, struct bch_sb_field *f
> > >  		return -BCH_ERR_ENOMEM_sb_journal_v2_validate;
> > >  
> > >  	for (i = 0; i < nr; i++) {
> > > +		entry_nr = le64_to_cpu(journal->d[i].nr);
> > > +		if (entry_nr > UINT_MAX) {
> > > +			prt_printf(err, "Journal v2 entry d[%u] nr %llu overflow\n",
> > > +				i, entry_nr);
> > > +			goto err;
> > > +		}
> > 
> > This check is unnecessary; we know the sum can't overflow a u64 because
> > we're also checking that the entries are nonoverlapping.
> You didn't read my previous email carefully.
> In this issue, journal->d[0] is 7, journal->d[1] is 18446744073709551615,
> so the sum of their u64 type values will definitely overflow.

It doesn't matter. We're already checking that the entries are
nonoverlapping, and within the range of [1, nbuckets), so total_nr can't
overflow nbuckets, much less an s64 (not that that matters).
Re: [PATCH V3] bcachefs: Add journal v2 entry nr value check
Posted by Lizhi Xu 1 year, 5 months ago 
On Tue, 20 Aug 2024 23:16:50 -0400, Lizhi Xu wrote:
> > On Tue, 20 Aug 2024 23:00:05 -0400, Kent Overstreet wrote:
> > > > When the nr value of a signle entry or their sum overflows, it will
> > > > cause the value of ja->nr to be incorrect, this will result in the
> > > > allocated memory to ja->buckets being too small, leading to out of
> > > > bounds access in bch2_dev_journal_init.
> > > >
> > > > Reported-by: syzbot+47ecc948aadfb2ab3efc@syzkaller.appspotmail.com
> > > > Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
> > > > ---
> > > >  fs/bcachefs/journal_sb.c | 16 +++++++++++++++-
> > > >  1 file changed, 15 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/fs/bcachefs/journal_sb.c b/fs/bcachefs/journal_sb.c
> > > > index db80e506e3ab..230ed99130e4 100644
> > > > --- a/fs/bcachefs/journal_sb.c
> > > > +++ b/fs/bcachefs/journal_sb.c
> > > > @@ -107,6 +107,7 @@ static int bch2_sb_journal_v2_validate(struct bch_sb *sb, struct bch_sb_field *f
> > > >  	unsigned nr;
> > > >  	unsigned i;
> > > >  	struct u64_range *b;
> > > > +	u64 total_nr = 0, entry_nr;
> > > >
> > > >  	nr = bch2_sb_field_journal_v2_nr_entries(journal);
> > > >  	if (!nr)
> > > > @@ -117,8 +118,21 @@ static int bch2_sb_journal_v2_validate(struct bch_sb *sb, struct bch_sb_field *f
> > > >  		return -BCH_ERR_ENOMEM_sb_journal_v2_validate;
> > > >
> > > >  	for (i = 0; i < nr; i++) {
> > > > +		entry_nr = le64_to_cpu(journal->d[i].nr);
> > > > +		if (entry_nr > UINT_MAX) {
> > > > +			prt_printf(err, "Journal v2 entry d[%u] nr %llu overflow\n",
> > > > +				i, entry_nr);
> > > > +			goto err;
> > > > +		}
> > >
> > > This check is unnecessary; we know the sum can't overflow a u64 because
> > > we're also checking that the entries are nonoverlapping.
> > You didn't read my previous email carefully.
> > In this issue, journal->d[0] is 7, journal->d[1] is 18446744073709551615,
> > so the sum of their u64 type values will definitely overflow.
> 
> It doesn't matter. We're already checking that the entries are
> nonoverlapping, and within the range of [1, nbuckets), so total_nr can't
> overflow nbuckets, much less an s64 (not that that matters).
Are you sure? Or did I not express myself clearly? See the actual running results below:
le64_to_cpu(journal->d[1].nr) + le64_to_cpu(journal->d[0].nr) = 7 + 18446744073709551615 will overflow.

When a u64 overflow occurs, total_nr will not be greater than UINT_MAX,
so it is not enough to only calculate the total nr of entry to determine.

Note: u64 contains 0 ~ 18446744073709551616.

BR,
Lizhi
Re: [PATCH V3] bcachefs: Add journal v2 entry nr value check
Posted by Kent Overstreet 1 year, 5 months ago 
On Tue, Aug 20, 2024 at 11:16:55PM GMT, Kent Overstreet wrote:
> On Wed, Aug 21, 2024 at 11:10:00AM GMT, Lizhi Xu wrote:
> > On Tue, 20 Aug 2024 23:00:05 -0400, Kent Overstreet wrote:
> > > > When the nr value of a signle entry or their sum overflows, it will
> > > > cause the value of ja->nr to be incorrect, this will result in the
> > > > allocated memory to ja->buckets being too small, leading to out of
> > > > bounds access in bch2_dev_journal_init.
> > > > 
> > > > Reported-by: syzbot+47ecc948aadfb2ab3efc@syzkaller.appspotmail.com
> > > > Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
> > > > ---
> > > >  fs/bcachefs/journal_sb.c | 16 +++++++++++++++-
> > > >  1 file changed, 15 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/fs/bcachefs/journal_sb.c b/fs/bcachefs/journal_sb.c
> > > > index db80e506e3ab..230ed99130e4 100644
> > > > --- a/fs/bcachefs/journal_sb.c
> > > > +++ b/fs/bcachefs/journal_sb.c
> > > > @@ -107,6 +107,7 @@ static int bch2_sb_journal_v2_validate(struct bch_sb *sb, struct bch_sb_field *f
> > > >  	unsigned nr;
> > > >  	unsigned i;
> > > >  	struct u64_range *b;
> > > > +	u64 total_nr = 0, entry_nr;
> > > >  
> > > >  	nr = bch2_sb_field_journal_v2_nr_entries(journal);
> > > >  	if (!nr)
> > > > @@ -117,8 +118,21 @@ static int bch2_sb_journal_v2_validate(struct bch_sb *sb, struct bch_sb_field *f
> > > >  		return -BCH_ERR_ENOMEM_sb_journal_v2_validate;
> > > >  
> > > >  	for (i = 0; i < nr; i++) {
> > > > +		entry_nr = le64_to_cpu(journal->d[i].nr);
> > > > +		if (entry_nr > UINT_MAX) {
> > > > +			prt_printf(err, "Journal v2 entry d[%u] nr %llu overflow\n",
> > > > +				i, entry_nr);
> > > > +			goto err;
> > > > +		}
> > > 
> > > This check is unnecessary; we know the sum can't overflow a u64 because
> > > we're also checking that the entries are nonoverlapping.
> > You didn't read my previous email carefully.
> > In this issue, journal->d[0] is 7, journal->d[1] is 18446744073709551615,
> > so the sum of their u64 type values will definitely overflow.
> 
> It doesn't matter. We're already checking that the entries are
> nonoverlapping, and within the range of [1, nbuckets), so total_nr can't
> overflow nbuckets, much less an s64 (not that that matters).

The check that's missing is that start + nr doesn't overflow, when we
convert to u64_ranges.

Patchew 2.1-devel-b67e4c2

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