83 lines
2.9 KiB
Diff
83 lines
2.9 KiB
Diff
From 51b8dca866a1b77a9803ee3b56e059f8e7795dd8 Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Wed, 26 Mar 2014 13:06:07 +0100
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Subject: [PATCH] qcow2: Limit snapshot table size
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Even with a limit of 64k snapshots, each snapshot could have a filename
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and an ID with up to 64k, which would still lead to pretty large
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allocations, which could potentially lead to qemu aborting. Limit the
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total size of the snapshot table to an average of 1k per entry when
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the limit of 64k snapshots is fully used. This should be plenty for any
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reasonable user.
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This also fixes potential integer overflows of s->snapshot_size.
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Suggested-by: Max Reitz <mreitz@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Reviewed-by: Max Reitz <mreitz@redhat.com>
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit 5dae6e30c531feb31eed99f9039b52bf70832ce3)
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---
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block/qcow2-snapshot.c | 15 ++++++++++++++-
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block/qcow2.h | 4 ++++
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2 files changed, 18 insertions(+), 1 deletion(-)
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diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
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index d2c956c..5d3c0e6 100644
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--- a/block/qcow2-snapshot.c
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+++ b/block/qcow2-snapshot.c
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@@ -116,8 +116,14 @@ int qcow2_read_snapshots(BlockDriverState *bs)
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}
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offset += name_size;
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sn->name[name_size] = '\0';
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+
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+ if (offset - s->snapshots_offset > QCOW_MAX_SNAPSHOTS_SIZE) {
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+ ret = -EFBIG;
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+ goto fail;
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+ }
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}
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+ assert(offset - s->snapshots_offset <= INT_MAX);
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s->snapshots_size = offset - s->snapshots_offset;
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return 0;
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@@ -138,7 +144,7 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
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uint32_t nb_snapshots;
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uint64_t snapshots_offset;
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} QEMU_PACKED header_data;
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- int64_t offset, snapshots_offset;
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+ int64_t offset, snapshots_offset = 0;
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int ret;
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/* compute the size of the snapshots */
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@@ -150,7 +156,14 @@ static int qcow2_write_snapshots(BlockDriverState *bs)
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offset += sizeof(extra);
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offset += strlen(sn->id_str);
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offset += strlen(sn->name);
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+
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+ if (offset > QCOW_MAX_SNAPSHOTS_SIZE) {
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+ ret = -EFBIG;
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+ goto fail;
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+ }
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}
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+
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+ assert(offset <= INT_MAX);
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snapshots_size = offset;
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/* Allocate space for the new snapshot list */
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diff --git a/block/qcow2.h b/block/qcow2.h
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index 0912488..797c9d8 100644
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--- a/block/qcow2.h
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+++ b/block/qcow2.h
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@@ -48,6 +48,10 @@
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* (128 GB for 512 byte clusters, 2 EB for 2 MB clusters) */
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#define QCOW_MAX_L1_SIZE 0x2000000
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+/* Allow for an average of 1k per snapshot table entry, should be plenty of
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+ * space for snapshot names and IDs */
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+#define QCOW_MAX_SNAPSHOTS_SIZE (1024 * QCOW_MAX_SNAPSHOTS)
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+
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/* indicate that the refcount of the referenced cluster is exactly one. */
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#define QCOW_OFLAG_COPIED (1LL << 63)
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/* indicate that the cluster is compressed (they never have the copied flag) */
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