diff options
| author | Mikulas Patocka <mpatocka@redhat.com> | 2026-07-01 18:13:50 +0200 |
|---|---|---|
| committer | Mikulas Patocka <mpatocka@redhat.com> | 2026-07-08 22:33:34 +0200 |
| commit | 31d6e6c0ba8d5a7bd59660035a089307100c5e8e (patch) | |
| tree | 341c8bbd73462f8fcf8c093b8299e23b52df0dc8 /drivers/md | |
| parent | a868196f03c2b19418ae3d2b69e195d668a271e5 (diff) | |
dm-verity: fix buffer overflow in FEC calculation
There's a buffer overflow in dm-verity-fec:
if (neras && *neras <= v->fec->roots)
fio->erasures[(*neras)++] = i;
This allows *neras to reach roots + 1 (the post-increment pushes it past
roots). This value is then passed as no_eras to decode_rs8(). Inside the
RS decoder (lib/reed_solomon/decode_rs.c:113-121), the erasure locator
polynomial loop writes lambda[j] where j can reach nroots + 1 — one
element past the end of lambda[] (which is sized nroots + 1, valid
indices 0..nroots). The out-of-bounds write lands on syn[0], corrupting
the syndrome buffer.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Assisted-by: Claude:claude-opus-4-6
Cc: stable@vger.kernel.org
Fixes: a739ff3f543a ("dm verity: add support for forward error correction")
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Diffstat (limited to 'drivers/md')
| -rw-r--r-- | drivers/md/dm-verity-fec.c | 4 | ||||
| -rw-r--r-- | drivers/md/dm-verity-fec.h | 2 |
2 files changed, 3 insertions, 3 deletions
diff --git a/drivers/md/dm-verity-fec.c b/drivers/md/dm-verity-fec.c index 85ad9dc210ff..c79f60df3a90 100644 --- a/drivers/md/dm-verity-fec.c +++ b/drivers/md/dm-verity-fec.c @@ -220,7 +220,7 @@ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io, PTR_ERR(bbuf)); /* assume the block is corrupted */ - if (neras && *neras <= v->fec->roots) + if (neras && *neras < v->fec->roots) fio->erasures[(*neras)++] = i; continue; @@ -238,7 +238,7 @@ static int fec_read_bufs(struct dm_verity *v, struct dm_verity_io *io, * skip if we have already found the theoretical * maximum number (i.e. fec->roots) of erasures */ - if (neras && *neras <= v->fec->roots && + if (neras && *neras < v->fec->roots && fec_is_erasure(v, io, want_digest, bbuf)) fio->erasures[(*neras)++] = i; } diff --git a/drivers/md/dm-verity-fec.h b/drivers/md/dm-verity-fec.h index 50b5e187d5cc..3885b514fc23 100644 --- a/drivers/md/dm-verity-fec.h +++ b/drivers/md/dm-verity-fec.h @@ -47,7 +47,7 @@ struct dm_verity_fec { /* per-bio data */ struct dm_verity_fec_io { struct rs_control *rs; /* Reed-Solomon state */ - int erasures[DM_VERITY_FEC_MAX_ROOTS + 1]; /* erasures for decode_rs8 */ + int erasures[DM_VERITY_FEC_MAX_ROOTS]; /* erasures for decode_rs8 */ u8 *output; /* buffer for corrected output */ unsigned int level; /* recursion level */ unsigned int nbufs; /* number of buffers allocated */ |