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dm: table detect io beyond device

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This patch fixes a panic on shrinking a DM device if there is
outstanding I/O to the part of the device that is being removed.
(Normally this doesn't happen - a filesystem would be resized first,
for example.)

The bug is that __clone_and_map() assumes dm_table_find_target()
always returns a valid pointer.  It may fail if a bio arrives from the
block layer but its target sector is no longer included in the DM
btree.

This patch appends an empty entry to table->targets[] which will
be returned by a lookup beyond the end of the device.

After calling dm_table_find_target(), __clone_and_map() and target_message()
check for this condition using
dm_target_is_valid().

Sample test script to trigger oops:
This commit is contained in:
Jun'ichi Nomura
2007-12-13 14:15:25 +00:00
committed by Alasdair G Kergon
parent fbdcf18df7
commit 512875bd96
4 changed files with 32 additions and 14 deletions
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10
drivers/md/dm-ioctl.c
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@@ -1250,21 +1250,17 @@ static int target_message(struct dm_ioctl *param, size_t param_size)
if (!table)
goto out_argv;
if (tmsg->sector >= dm_table_get_size(table)) {
ti = dm_table_find_target(table, tmsg->sector);
if (!dm_target_is_valid(ti)) {
DMWARN("Target message sector outside device.");
r = -EINVAL;
goto out_table;
}
ti = dm_table_find_target(table, tmsg->sector);
if (ti->type->message)
} else if (ti->type->message)
r = ti->type->message(ti, argc, argv);
else {
DMWARN("Target type does not support messages");
r = -EINVAL;
}
out_table:
dm_table_put(table);
out_argv:
kfree(argv);