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From 71ac1ab735eeaa71af0198253c06f783c8582362 Mon Sep 17 00:00:00 2001
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From: Torsten Hilbrich <torsten.hilbrich@secunet.com>
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Date: Mon, 20 Jun 2016 07:09:10 +0200
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Subject: [PATCH 194/197] liblkid: Add length check in probe_nilfs2 before
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crc32
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The bytes variable is read from the file system to probe and must be
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checked before used as length parameter in the crc32 call.
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The following problems may occur here:
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- bytes smaller than sumoff + 4: underflow in length calculation
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- bytes larger than remaining space in sb: overflow of buffer
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This fixes a problem where an encrypted volume had the correct magic
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values 0x3434 at offset 0x406 and the following uint16_t (which is
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read into the nilfs_super_block.s_bytes struct) was parsed as 1.
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Then crc32 was called with the length value 18446744073709551597
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causing a segmentation fault.
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[kzak@redhat.com: - fix probe_nilfs2() return code
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- RHEL-7: return 1 if superblock bytes are out if
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range; we use the same for invalid superblock in
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current upstream tree]
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Upstream: http://github.com/karelzak/util-linux/commit/ac681a310c32319423297544833932f4d689a7a2
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Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1802240
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Signed-off-by: Karel Zak <kzak@redhat.com>
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---
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libblkid/src/superblocks/nilfs.c | 9 ++++++++-
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1 file changed, 8 insertions(+), 1 deletion(-)
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diff --git a/libblkid/src/superblocks/nilfs.c b/libblkid/src/superblocks/nilfs.c
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index a7e4939a2..a4b3c22b6 100644
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--- a/libblkid/src/superblocks/nilfs.c
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+++ b/libblkid/src/superblocks/nilfs.c
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@@ -78,6 +78,7 @@ static int probe_nilfs2(blkid_probe pr, const struct blkid_idmag *mag)
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static unsigned char sum[4];
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const int sumoff = offsetof(struct nilfs_super_block, s_sum);
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size_t bytes;
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+ const size_t crc_start = sumoff + 4;
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uint32_t crc;
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sb = blkid_probe_get_sb(pr, mag, struct nilfs_super_block);
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@@ -85,9 +86,15 @@ static int probe_nilfs2(blkid_probe pr, const struct blkid_idmag *mag)
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return errno ? -errno : 1;
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bytes = le16_to_cpu(sb->s_bytes);
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+ /* ensure that no underrun can happen in the length parameter
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+ * of the crc32 call or more data are processed than read into
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+ * sb */
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+ if (bytes < crc_start || bytes > sizeof(struct nilfs_super_block))
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+ return 1;
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+
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crc = crc32(le32_to_cpu(sb->s_crc_seed), (unsigned char *)sb, sumoff);
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crc = crc32(crc, sum, 4);
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- crc = crc32(crc, (unsigned char *)sb + sumoff + 4, bytes - sumoff - 4);
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+ crc = crc32(crc, (unsigned char *)sb + crc_start, bytes - crc_start);
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if (crc != le32_to_cpu(sb->s_sum))
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return 1;
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--
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2.25.2
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