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From dc4ff14029538f4f2787271b98d6e8e403cbfcc5 Mon Sep 17 00:00:00 2001
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From: Jon Maloy <jmaloy@redhat.com>
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Date: Fri, 26 Feb 2021 01:06:42 -0500
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Subject: [PATCH] ide: atapi: check logical block address and read size
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 (CVE-2020-29443)
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RH-Author: Jon Maloy <jmaloy@redhat.com>
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Message-id: <20210226010642.3200257-2-jmaloy@redhat.com>
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Patchwork-id: 101270
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O-Subject: [RHEL-7.9.z qemu-kvm PATCH v2 1/1] ide: atapi: check logical block address and read size (CVE-2020-29443)
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Bugzilla: 1917449
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RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
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RH-Acked-by: Danilo de Paula <ddepaula@redhat.com>
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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From: Prasad J Pandit <pjp@fedoraproject.org>
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While processing ATAPI cmd_read/cmd_read_cd commands,
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Logical Block Address (LBA) maybe invalid OR closer to the last block,
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leading to an OOB access issues. Add range check to avoid it.
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Fixes: CVE-2020-29443
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Reported-by: Wenxiang Qian <leonwxqian@gmail.com>
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Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
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Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
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Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
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Message-Id: <20210118115130.457044-1-ppandit@redhat.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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(cherry picked from commit b8d7f1bc59276fec85e4d09f1567613a3e14d31e)
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Conflict: There is a conflict in cmd_read_cd(), because
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commit e7bd708ec85e ("atapi: classify read_cd as conditionally
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returning data") is missing in this code version. That seems to be an
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unrelated fix that drags in further changes, so instead of applying it
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we choose to adapt the commit directly to the current code version.
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Signed-off-by: Jon Maloy <jmaloy@redhat.com>
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Signed-off-by: Jon Maloy <jmaloy.redhat.com>
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---
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 hw/ide/atapi.c | 29 ++++++++++++++++++++++++-----
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 1 file changed, 24 insertions(+), 5 deletions(-)
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diff --git a/hw/ide/atapi.c b/hw/ide/atapi.c
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index 490070a1b4..bef74914d1 100644
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--- a/hw/ide/atapi.c
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+++ b/hw/ide/atapi.c
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@@ -267,6 +267,8 @@ static void ide_atapi_cmd_reply(IDEState *s, int size, int max_size)
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 static void ide_atapi_cmd_read_pio(IDEState *s, int lba, int nb_sectors,
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                                    int sector_size)
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 {
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+    assert(0 <= lba && lba < (s->nb_sectors >> 2));
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+
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     s->lba = lba;
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     s->packet_transfer_size = nb_sectors * sector_size;
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     s->elementary_transfer_size = 0;
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@@ -365,6 +367,8 @@ eot:
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 static void ide_atapi_cmd_read_dma(IDEState *s, int lba, int nb_sectors,
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                                    int sector_size)
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 {
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+    assert(0 <= lba && lba < (s->nb_sectors >> 2));
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+
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     s->lba = lba;
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     s->packet_transfer_size = nb_sectors * sector_size;
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     s->io_buffer_index = 0;
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@@ -823,7 +827,10 @@ static void cmd_prevent_allow_medium_removal(IDEState *s, uint8_t* buf)
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 static void cmd_read(IDEState *s, uint8_t* buf)
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 {
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-    int nb_sectors, lba;
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+    unsigned int nb_sectors, lba;
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+
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+    /* Total logical sectors of ATAPI_SECTOR_SIZE(=2048) bytes */
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+    uint64_t total_sectors = s->nb_sectors >> 2;
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     if (buf[0] == GPCMD_READ_10) {
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         nb_sectors = ube16_to_cpu(buf + 7);
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@@ -831,27 +838,39 @@ static void cmd_read(IDEState *s, uint8_t* buf)
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         nb_sectors = ube32_to_cpu(buf + 6);
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     }
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-    lba = ube32_to_cpu(buf + 2);
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     if (nb_sectors == 0) {
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         ide_atapi_cmd_ok(s);
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         return;
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     }
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+    lba = ldl_be_p(buf + 2);
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+    if (lba >= total_sectors || lba + nb_sectors - 1 >= total_sectors) {
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+        ide_atapi_cmd_error(s, ILLEGAL_REQUEST, ASC_LOGICAL_BLOCK_OOR);
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+        return;
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+    }
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+
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     ide_atapi_cmd_read(s, lba, nb_sectors, 2048);
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 }
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 static void cmd_read_cd(IDEState *s, uint8_t* buf)
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 {
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-    int nb_sectors, lba, transfer_request;
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+    unsigned int nb_sectors, lba, transfer_request;
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-    nb_sectors = (buf[6] << 16) | (buf[7] << 8) | buf[8];
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-    lba = ube32_to_cpu(buf + 2);
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+    /* Total logical sectors of ATAPI_SECTOR_SIZE(=2048) bytes */
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+    uint64_t total_sectors = s->nb_sectors >> 2;
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+    nb_sectors = (buf[6] << 16) | (buf[7] << 8) | buf[8];
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     if (nb_sectors == 0) {
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         ide_atapi_cmd_ok(s);
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         return;
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     }
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+    lba = ldl_be_p(buf + 2);
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+    if (lba >= total_sectors || lba + nb_sectors - 1 >= total_sectors) {
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+        ide_atapi_cmd_error(s, ILLEGAL_REQUEST, ASC_LOGICAL_BLOCK_OOR);
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+        return;
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+    }
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+
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     transfer_request = buf[9];
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     switch(transfer_request & 0xf8) {
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     case 0x00:
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-- 
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2.18.2
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