* Re: [PATCH] bcachefs: guard against invalid bits_per_field in bch2_bkey_format_invalid
2024-05-09 1:40 [PATCH] bcachefs: guard against invalid bits_per_field in bch2_bkey_format_invalid Camila Alvarez
@ 2024-05-09 19:32 ` Kent Overstreet
0 siblings, 0 replies; 2+ messages in thread
From: Kent Overstreet @ 2024-05-09 19:32 UTC (permalink / raw)
To: Camila Alvarez
Cc: Brian Foster, linux-bcachefs, linux-kernel, syzbot+9833a1d29d4a44361e2c
On Wed, May 08, 2024 at 09:40:32PM -0400, Camila Alvarez wrote:
> A check for a valid value for bits_per_field is performed for each field before computing packed_max.
> If bits_per_field is invalid for any field the whole format is deemed
> invalid.
>
> Reported-by: syzbot+9833a1d29d4a44361e2c@syzkaller.appspotmail.com
> Signed-off-by: Camila Alvarez <cam.alvarez.i@gmail.com>
> ---
> fs/bcachefs/bcachefs_format.h | 8 ++++++++
> fs/bcachefs/bkey.c | 18 ++++++++++++++++--
> 2 files changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/fs/bcachefs/bcachefs_format.h b/fs/bcachefs/bcachefs_format.h
> index d5b90439e581..9e688a8d780f 100644
> --- a/fs/bcachefs/bcachefs_format.h
> +++ b/fs/bcachefs/bcachefs_format.h
> @@ -318,6 +318,14 @@ enum bch_bkey_fields {
> #define bkey_format_field(name, field) \
> [BKEY_FIELD_##name] = (sizeof(((struct bkey *) NULL)->field) * 8)
>
> +#define BCH_BKEY_FIELDS() \
> + x(INODE, p.inode) \
> + x(OFFSET, p.offset) \
> + x(SNAPSHOT, p.snapshot) \
> + x(SIZE, size) \
> + x(VERSION_HI, version.hi) \
> + x(VERSION_LO, version.lo)
> +
> #define BKEY_FORMAT_CURRENT \
> ((struct bkey_format) { \
> .key_u64s = BKEY_U64s, \
> diff --git a/fs/bcachefs/bkey.c b/fs/bcachefs/bkey.c
> index 76e79a15ba08..f7847c96a105 100644
> --- a/fs/bcachefs/bkey.c
> +++ b/fs/bcachefs/bkey.c
> @@ -638,6 +638,13 @@ struct bkey_format bch2_bkey_format_done(struct bkey_format_state *s)
> return ret;
> }
>
> +static unsigned bch2_max_bits_per_field[] = {
> +#define x(name, field) \
> + bkey_format_field(name, field),
> + BCH_BKEY_FIELDS()
> +#undef x
> +};
> +
> int bch2_bkey_format_invalid(struct bch_fs *c,
> struct bkey_format *f,
> enum bkey_invalid_flags flags,
> @@ -659,8 +666,15 @@ int bch2_bkey_format_invalid(struct bch_fs *c,
> if (!c || c->sb.version_min >= bcachefs_metadata_version_snapshot) {
> unsigned unpacked_bits = bch2_bkey_format_current.bits_per_field[i];
> u64 unpacked_max = ~((~0ULL << 1) << (unpacked_bits - 1));
> - u64 packed_max = f->bits_per_field[i]
> - ? ~((~0ULL << 1) << (f->bits_per_field[i] - 1))
> + unsigned bits_per_field = f->bits_per_field[i];
> +
> + if (bits_per_field > bch2_max_bits_per_field[i]) {
> + prt_printf(err, "field %u uses more bits than allowed: %u > %u",
> + i, bits_per_field, bch2_max_bits_per_field[i]);
> + return -BCH_ERR_invalid;
> + }
> + u64 packed_max = bits_per_field
> + ? ~((~0ULL << 1) << (bits_per_field - 1))
> : 0;
> u64 field_offset = le64_to_cpu(f->field_offset[i]);
>
> --
> 2.34.1
>
Already applied this patch:
commit 61692c7812ab2aca17a3751f6e7798acbdae4b6b
Author: Kent Overstreet <kent.overstreet@linux.dev>
Date: Wed May 8 10:58:26 2024 -0400
bcachefs: bch2_bkey_format_field_overflows()
Fix another shift-by-64 by factoring out a common helper for
bch2_bkey_format_invalid() and bformat_needs_redo() (where it was
already fixed).
Reported-by: syzbot+9833a1d29d4a44361e2c@syzkaller.appspotmail.com
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
diff --git a/fs/bcachefs/bkey.c b/fs/bcachefs/bkey.c
index 76e79a15ba08..952299a2e416 100644
--- a/fs/bcachefs/bkey.c
+++ b/fs/bcachefs/bkey.c
@@ -656,20 +656,17 @@ int bch2_bkey_format_invalid(struct bch_fs *c,
* unpacked format:
*/
for (i = 0; i < f->nr_fields; i++) {
- if (!c || c->sb.version_min >= bcachefs_metadata_version_snapshot) {
+ if ((!c || c->sb.version_min >= bcachefs_metadata_version_snapshot) &&
+ bch2_bkey_format_field_overflows(f, i)) {
unsigned unpacked_bits = bch2_bkey_format_current.bits_per_field[i];
u64 unpacked_max = ~((~0ULL << 1) << (unpacked_bits - 1));
u64 packed_max = f->bits_per_field[i]
? ~((~0ULL << 1) << (f->bits_per_field[i] - 1))
: 0;
- u64 field_offset = le64_to_cpu(f->field_offset[i]);
- if (packed_max + field_offset < packed_max ||
- packed_max + field_offset > unpacked_max) {
- prt_printf(err, "field %u too large: %llu + %llu > %llu",
- i, packed_max, field_offset, unpacked_max);
- return -BCH_ERR_invalid;
- }
+ prt_printf(err, "field %u too large: %llu + %llu > %llu",
+ i, packed_max, le64_to_cpu(f->field_offset[i]), unpacked_max);
+ return -BCH_ERR_invalid;
}
bits += f->bits_per_field[i];
diff --git a/fs/bcachefs/bkey.h b/fs/bcachefs/bkey.h
index 3a45d128f608..1bb0bd4371b0 100644
--- a/fs/bcachefs/bkey.h
+++ b/fs/bcachefs/bkey.h
@@ -574,6 +574,29 @@ static inline void bch2_bkey_format_add_key(struct bkey_format_state *s, const s
void bch2_bkey_format_add_pos(struct bkey_format_state *, struct bpos);
struct bkey_format bch2_bkey_format_done(struct bkey_format_state *);
+
+static inline bool bch2_bkey_format_field_overflows(struct bkey_format *f, unsigned i)
+{
+ unsigned f_bits = f->bits_per_field[i];
+ unsigned unpacked_bits = bch2_bkey_format_current.bits_per_field[i];
+ u64 unpacked_mask = ~((~0ULL << 1) << (unpacked_bits - 1));
+ u64 field_offset = le64_to_cpu(f->field_offset[i]);
+
+ if (f_bits > unpacked_bits)
+ return true;
+
+ if ((f_bits == unpacked_bits) && field_offset)
+ return true;
+
+ u64 f_mask = f_bits
+ ? ~((~0ULL << (f_bits - 1)) << 1)
+ : 0;
+
+ if (((field_offset + f_mask) & unpacked_mask) < field_offset)
+ return true;
+ return false;
+}
+
int bch2_bkey_format_invalid(struct bch_fs *, struct bkey_format *,
enum bkey_invalid_flags, struct printbuf *);
void bch2_bkey_format_to_text(struct printbuf *, const struct bkey_format *);
diff --git a/fs/bcachefs/move.c b/fs/bcachefs/move.c
index 4d94b7742dbb..45984a688e5b 100644
--- a/fs/bcachefs/move.c
+++ b/fs/bcachefs/move.c
@@ -975,26 +975,10 @@ static bool migrate_btree_pred(struct bch_fs *c, void *arg,
*/
static bool bformat_needs_redo(struct bkey_format *f)
{
- for (unsigned i = 0; i < f->nr_fields; i++) {
- unsigned f_bits = f->bits_per_field[i];
- unsigned unpacked_bits = bch2_bkey_format_current.bits_per_field[i];
- u64 unpacked_mask = ~((~0ULL << 1) << (unpacked_bits - 1));
- u64 field_offset = le64_to_cpu(f->field_offset[i]);
-
- if (f_bits > unpacked_bits)
- return true;
-
- if ((f_bits == unpacked_bits) && field_offset)
+ for (unsigned i = 0; i < f->nr_fields; i++)
+ if (bch2_bkey_format_field_overflows(f, i))
return true;
- u64 f_mask = f_bits
- ? ~((~0ULL << (f_bits - 1)) << 1)
- : 0;
-
- if (((field_offset + f_mask) & unpacked_mask) < field_offset)
- return true;
- }
-
return false;
}
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