Hi Michael,
On Fri, Oct 12, 2018 at 2:27 AM Michael Schmitz <schmitzmic@xxxxxxxxx> wrote:
The Amiga partition parser module uses signed int for partition sector
address and count, which will overflow for disks larger than 1 TB.
Use u64 as type for sector address and size to allow using disks up to
2 TB without LBD support, and disks larger than 2 TB with LBD. The RBD
format allows to specify disk sizes up to 2^128 bytes (though native
OS limitations reduce this somewhat, to max 2^68 bytes), so check for
u64 overflow carefully to protect against overflowing sector_t.
Bail out if sector addresses overflow 32 bits on kernels without LBD
support.
This bug was reported originally in 2012, and the fix was created by
the RDB author, Joanne Dow <jdow@xxxxxxxxxxxxx>. A patch had been
discussed and reviewed on linux-m68k at that time but never officially
submitted (now resubmitted as separate patch).
This patch adds additional error checking and warning messages.
Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=43511
Reported-by: Martin Steigerwald <Martin@xxxxxxxxxxxx>
Message-ID: <201206192146.09327.Martin@xxxxxxxxxxxx>
Signed-off-by: Michael Schmitz <schmitzmic@xxxxxxxxx>
Thanks for being persistent!
BTW, there's another possible overflow in "blk *= blksize", but that one
is very unlikely to happen, as most (all?) partitioners store partition
blocks close to the beginning of the disk.
--- a/block/partitions/amiga.c
+++ b/block/partitions/amiga.c
@@ -32,9 +40,12 @@ int amiga_partition(struct parsed_partitions *state)
unsigned char *data;
struct RigidDiskBlock *rdb;
struct PartitionBlock *pb;
- sector_t start_sect, nr_sects;
+ u64 start_sect, nr_sects;
+ sector_t end_sect;
+ u32 cylblk; /* rdb_CylBlocks = nr_heads*sect_per_track */
+ u32 nr_hd, nr_sect, lo_cyl, hi_cyl;
int blk, part, res = 0;
- int blksize = 1; /* Multiplier for disk block size */
+ unsigned int blksize = 1; /* Multiplier for disk block size */
int slot = 1;
char b[BDEVNAME_SIZE];
@@ -99,19 +110,70 @@ int amiga_partition(struct parsed_partitions *state)
if (checksum_block((__be32 *)pb, be32_to_cpu(pb->pb_SummedLongs) & 0x7F) != 0 )
continue;
- /* Tell Kernel about it */
+ /* RDB gives us more than enough rope to hang ourselves with,
+ * many times over (2^128 bytes if all fields max out).
+ * Some careful checks are in order, so check for potential
+ * overflows.
+ * We are multiplying four 32 bit numbers to one sector_t!
+ */
+
+ nr_hd = be32_to_cpu(pb->pb_Environment[NR_HD]);
+ nr_sect = be32_to_cpu(pb->pb_Environment[NR_SECT]);
+
+ /* CylBlocks is total number of blocks per cylinder */
+ if (check_mul_overflow(nr_hd, nr_sect, &cylblk)) {
+ pr_err("Dev %s: heads*sects %u overflows u32, skipping partition!\n",
+ bdevname(state->bdev, b), cylblk);
+ continue;
+ }
+
+ /* check for consistency with RDB defined CylBlocks */
+ if (cylblk > be32_to_cpu(rdb->rdb_CylBlocks)) {
+ pr_warn("Dev %s: cylblk %u > rdb_CylBlocks %u!\n",
+ bdevname(state->bdev, b), cylblk,
+ be32_to_cpu(rdb->rdb_CylBlocks));
+ }
+
+ /* RDB allows for variable logical block size -
+ * normalize to 512 byte blocks and check result.
+ */
+
+ if (check_mul_overflow(cylblk, blksize, &cylblk)) {
+ pr_err("Dev %s: partition %u bytes per cyl. overflows u32, skipping partition!\n",
+ bdevname(state->bdev, b), part);
Unlike the comparison with 32-bit rdb_CylBlocks above, this is an
artificial limitation, right?
You can relax it by using 64-bit arithmetic, but that would complicate the
calculation of start_sect and nr_sects below, as they may overflow 64-bit.
+ continue;
+ }
+
+ /* Calculate partition start and end. Limit of 32 bit on cylblk
+ * guarantees no overflow occurs if LBD support is enabled.
+ */
+
+ lo_cyl = be32_to_cpu(pb->pb_Environment[LO_CYL]);
+ start_sect = (u64) (lo_cyl * cylblk);
As lo_cyl and cylblk are both u32, the multiplication will be done using
32-bit arithmetic, and may overflow. Hence you should cast one of the
multiplicands, instead of the result:
start_sect = ((u64)lo_cyl * cylblk);
+
+ hi_cyl = be32_to_cpu(pb->pb_Environment[HI_CYL]);
+ nr_sects = (u64) ((hi_cyl - lo_cyl + 1) * cylblk);
Likewise.
- nr_sects = ((sector_t) be32_to_cpu(pb->pb_Environment[10])
- + 1 - be32_to_cpu(pb->pb_Environment[9])) *
- be32_to_cpu(pb->pb_Environment[3]) *
- be32_to_cpu(pb->pb_Environment[5]) *
- blksize;
if (!nr_sects)
continue;
- start_sect = (sector_t) be32_to_cpu(pb->pb_Environment[9]) *
- be32_to_cpu(pb->pb_Environment[3]) *
- be32_to_cpu(pb->pb_Environment[5]) *
- blksize;
+
+ /* Warn user if partition end overflows u32 (AmigaDOS limit) */
+
+ if ((start_sect + nr_sects) > UINT_MAX) {
+ pr_warn("Dev %s: partition %u (%llu-%llu) needs 64 bit device support!\n",
+ bdevname(state->bdev, b), part,
+ start_sect, start_sect + nr_sects);
+ }
+
+ if (check_add_overflow(start_sect, nr_sects, &end_sect)) {
+ pr_err("Dev %s: partition %u (%llu-%llu) needs LBD device support, skipping partition!\n",
+ bdevname(state->bdev, b), part,
+ start_sect, (u64) end_sect);
The cast to u64 is not needed.
+ continue;
+ }
+
+ /* Tell Kernel about it */
+
put_partition(state,slot++,start_sect,nr_sects);
{
/* Be even more informative to aid mounting */
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
