[PATCH 45/64] hw/sd/sdcard: Fix assertion accessing out-of-range addresses with CMD30

[Michael Roth]

From: Philippe Mathieu-Daudé <f4bug@amsat.org>

OSS-Fuzz found sending illegal addresses when querying the write
protection bits triggers the assertion added in commit 84816fb63e5
("hw/sd/sdcard: Assert if accessing an illegal group"):

  qemu-fuzz-i386-target-generic-fuzz-sdhci-v3: ../hw/sd/sd.c:824: uint32_t 
sd_wpbits(SDState *, uint64_t):
  Assertion `wpnum < sd->wpgrps_size' failed.
  #3 0x7f62a8b22c91 in __assert_fail
  #4 0x5569adcec405 in sd_wpbits hw/sd/sd.c:824:9
  #5 0x5569adce5f6d in sd_normal_command hw/sd/sd.c:1389:38
  #6 0x5569adce3870 in sd_do_command hw/sd/sd.c:1737:17
  #7 0x5569adcf1566 in sdbus_do_command hw/sd/core.c:100:16
  #8 0x5569adcfc192 in sdhci_send_command hw/sd/sdhci.c:337:12
  #9 0x5569adcfa3a3 in sdhci_write hw/sd/sdhci.c:1186:9
  #10 0x5569adfb3447 in memory_region_write_accessor softmmu/memory.c:492:5

It is legal for the CMD30 to query for out-of-range addresses.
Such invalid addresses are simply ignored in the response (write
protection bits set to 0).

In commit 84816fb63e5 ("hw/sd/sdcard: Assert if accessing an illegal
group") we misplaced the assertion *before* we test the address is
in range. Move it *after*.

Include the qtest reproducer provided by Alexander Bulekov:

  $ make check-qtest-i386
  ...
  Running test qtest-i386/fuzz-sdcard-test
  qemu-system-i386: ../hw/sd/sd.c:824: sd_wpbits: Assertion `wpnum < 
sd->wpgrps_size' failed.

Cc: qemu-stable@nongnu.org
Reported-by: OSS-Fuzz (Issue 29225)
Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Fixes: 84816fb63e5 ("hw/sd/sdcard: Assert if accessing an illegal group")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/495
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20210802235524.3417739-3-f4bug@amsat.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Tested-by: Alexander Bulekov <alxndr@bu.edu>
(cherry picked from commit 4ac0b72bae85cf94ae0e5153b9c2c288c71667d4)
*drop fuzz test additions, since sdcard fuzz test has functional
 dependency on guest-visible change not flagged for stable:
 59b63d78 ("hw/sd/sdcard: Check for valid address range in SEND_WRITE_PROT 
(CMD30)")
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
 hw/sd/sd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/sd/sd.c b/hw/sd/sd.c
index fa6bb79b15..bc8f17ddf9 100644
--- a/hw/sd/sd.c
+++ b/hw/sd/sd.c
@@ -821,7 +821,6 @@ static uint32_t sd_wpbits(SDState *sd, uint64_t addr)
     wpnum = sd_addr_to_wpnum(addr);
 
     for (i = 0; i < 32; i++, wpnum++, addr += WPGROUP_SIZE) {
-        assert(wpnum < sd->wpgrps_size);
         if (addr >= sd->size) {
             /*
              * If the addresses of the last groups are outside the valid range,
@@ -829,6 +828,7 @@ static uint32_t sd_wpbits(SDState *sd, uint64_t addr)
              */
             continue;
         }
+        assert(wpnum < sd->wpgrps_size);
         if (test_bit(wpnum, sd->wp_groups)) {
             ret |= (1 << i);
         }
-- 
2.25.1