Hi
Here I'm submitting the updated patch for the 5.4 branch.
Mikulas
commit 5c02406428d5219c367c5f53457698c58bc5f917 Author: Mikulas Patocka mpatocka@redhat.com Date: Wed Jan 20 13:59:11 2021 -0500
dm integrity: conditionally disable "recalculate" feature
Otherwise a malicious user could (ab)use the "recalculate" feature that makes dm-integrity calculate the checksums in the background while the device is already usable. When the system restarts before all checksums have been calculated, the calculation continues where it was interrupted even if the recalculate feature is not requested the next time the dm device is set up.
Disable recalculating if we use internal_hash or journal_hash with a key (e.g. HMAC) and we don't have the "legacy_recalculate" flag.
This may break activation of a volume, created by an older kernel, that is not yet fully recalculated -- if this happens, the user should add the "legacy_recalculate" flag to constructor parameters.
Cc: stable@vger.kernel.org Signed-off-by: Mikulas Patocka mpatocka@redhat.com Reported-by: Daniel Glockner dg@emlix.com Signed-off-by: Mike Snitzer snitzer@redhat.com
Index: linux-stable/Documentation/admin-guide/device-mapper/dm-integrity.rst =================================================================== --- linux-stable.orig/Documentation/admin-guide/device-mapper/dm-integrity.rst +++ linux-stable/Documentation/admin-guide/device-mapper/dm-integrity.rst @@ -177,6 +177,12 @@ bitmap_flush_interval:number The bitmap flush interval in milliseconds. The metadata buffers are synchronized when this interval expires.
+legacy_recalculate + Allow recalculating of volumes with HMAC keys. This is disabled by + default for security reasons - an attacker could modify the volume, + set recalc_sector to zero, and the kernel would not detect the + modification. +
The journal mode (D/J), buffer_sectors, journal_watermark, commit_time can be changed when reloading the target (load an inactive table and swap the Index: linux-stable/drivers/md/dm-integrity.c =================================================================== --- linux-stable.orig/drivers/md/dm-integrity.c +++ linux-stable/drivers/md/dm-integrity.c @@ -254,6 +254,7 @@ struct dm_integrity_c { bool journal_uptodate; bool just_formatted; bool recalculate_flag; + bool legacy_recalculate;
struct alg_spec internal_hash_alg; struct alg_spec journal_crypt_alg; @@ -381,6 +382,14 @@ static int dm_integrity_failed(struct dm return READ_ONCE(ic->failed); }
+static bool dm_integrity_disable_recalculate(struct dm_integrity_c *ic) +{ + if ((ic->internal_hash_alg.key || ic->journal_mac_alg.key) && + !ic->legacy_recalculate) + return true; + return false; +} + static commit_id_t dm_integrity_commit_id(struct dm_integrity_c *ic, unsigned i, unsigned j, unsigned char seq) { @@ -2998,6 +3007,7 @@ static void dm_integrity_status(struct d arg_count += !!ic->internal_hash_alg.alg_string; arg_count += !!ic->journal_crypt_alg.alg_string; arg_count += !!ic->journal_mac_alg.alg_string; + arg_count += ic->legacy_recalculate; DMEMIT("%s %llu %u %c %u", ic->dev->name, (unsigned long long)ic->start, ic->tag_size, ic->mode, arg_count); if (ic->meta_dev) @@ -3017,6 +3027,8 @@ static void dm_integrity_status(struct d DMEMIT(" sectors_per_bit:%llu", (unsigned long long)ic->sectors_per_block << ic->log2_blocks_per_bitmap_bit); DMEMIT(" bitmap_flush_interval:%u", jiffies_to_msecs(ic->bitmap_flush_interval)); } + if (ic->legacy_recalculate) + DMEMIT(" legacy_recalculate");
#define EMIT_ALG(a, n) \ do { \ @@ -3625,7 +3637,7 @@ static int dm_integrity_ctr(struct dm_ta unsigned extra_args; struct dm_arg_set as; static const struct dm_arg _args[] = { - {0, 15, "Invalid number of feature args"}, + {0, 14, "Invalid number of feature args"}, }; unsigned journal_sectors, interleave_sectors, buffer_sectors, journal_watermark, sync_msec; bool should_write_sb; @@ -3769,6 +3781,8 @@ static int dm_integrity_ctr(struct dm_ta goto bad; } else if (!strcmp(opt_string, "recalculate")) { ic->recalculate_flag = true; + } else if (!strcmp(opt_string, "legacy_recalculate")) { + ic->legacy_recalculate = true; } else { r = -EINVAL; ti->error = "Invalid argument"; @@ -4061,6 +4075,14 @@ try_smaller_buffer: } }
+ if (ic->sb->flags & cpu_to_le32(SB_FLAG_RECALCULATING) && + le64_to_cpu(ic->sb->recalc_sector) < ic->provided_data_sectors && + dm_integrity_disable_recalculate(ic)) { + ti->error = "Recalculating with HMAC is disabled for security reasons - if you really need it, use the argument "legacy_recalculate""; + r = -EOPNOTSUPP; + goto bad; + } + ic->bufio = dm_bufio_client_create(ic->meta_dev ? ic->meta_dev->bdev : ic->dev->bdev, 1U << (SECTOR_SHIFT + ic->log2_buffer_sectors), 1, 0, NULL, NULL); if (IS_ERR(ic->bufio)) {