Re: [PATCH-for-6.1 2/3] hw/sd/sdcard: Fix assertion accessing out-of-range addresses with CMD30

[Philippe Mathieu-Daudé]

Peter, Bin, could you review this (trivial) patch?
This is a regression since 6.1 I'd like to get fixed
for v6.1.0-rc2.

On 7/28/21 8:17 PM, Philippe Mathieu-Daudé wrote:
> 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).
> 
> Note, we had an off-by-one in the wpgrps_size check since commit
> a1bb27b1e98. Since we have a total of 'wpgrps_size' bits, the latest
> valid group bit is 'wpgrps_size - 1'.
> 
> Since we now check the group bit is in range, remove the assertion.
> 
> 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)
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/495
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>  hw/sd/sd.c                     |  4 ++--
>  tests/qtest/fuzz-sdcard-test.c | 36 ++++++++++++++++++++++++++++++++++
>  2 files changed, 38 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/sd/sd.c b/hw/sd/sd.c
> index 707dcc12a14..273af75c1be 100644
> --- a/hw/sd/sd.c
> +++ b/hw/sd/sd.c
> @@ -820,8 +820,8 @@ 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);
> +    for (i = 0; i < 32 && wpnum < sd->wpgrps_size - 1;
> +                i++, wpnum++, addr += WPGROUP_SIZE) {
>          if (addr >= sd->size) {
>              /*
>               * If the addresses of the last groups are outside the valid 
> range,
> diff --git a/tests/qtest/fuzz-sdcard-test.c b/tests/qtest/fuzz-sdcard-test.c
> index 96602eac7e5..ae14305344a 100644
> --- a/tests/qtest/fuzz-sdcard-test.c
> +++ b/tests/qtest/fuzz-sdcard-test.c
> @@ -52,6 +52,41 @@ static void oss_fuzz_29225(void)
>      qtest_quit(s);
>  }
>  
> +/*
> + * https://gitlab.com/qemu-project/qemu/-/issues/495
> + * Used to trigger:
> + *  Assertion `wpnum < sd->wpgrps_size' failed.
> + */
> +static void oss_fuzz_36217(void)
> +{
> +    QTestState *s;
> +
> +    s = qtest_init(" -display none -m 32 -nodefaults -nographic"
> +                   " -device sdhci-pci,sd-spec-version=3 "
> +                   "-device sd-card,drive=d0 "
> +                   "-drive 
> if=none,index=0,file=null-co://,format=raw,id=d0");
> +
> +    qtest_outl(s, 0xcf8, 0x80001010);
> +    qtest_outl(s, 0xcfc, 0xe0000000);
> +    qtest_outl(s, 0xcf8, 0x80001004);
> +    qtest_outw(s, 0xcfc, 0x02);
> +    qtest_bufwrite(s, 0xe000002c, "\x05", 0x1);
> +    qtest_bufwrite(s, 0xe000000f, "\x37", 0x1);
> +    qtest_bufwrite(s, 0xe000000a, "\x01", 0x1);
> +    qtest_bufwrite(s, 0xe000000f, "\x29", 0x1);
> +    qtest_bufwrite(s, 0xe000000f, "\x02", 0x1);
> +    qtest_bufwrite(s, 0xe000000f, "\x03", 0x1);
> +    qtest_bufwrite(s, 0xe0000005, "\x01", 0x1);
> +    qtest_bufwrite(s, 0xe000000f, "\x06", 0x1);
> +    qtest_bufwrite(s, 0xe000000c, "\x05", 0x1);
> +    qtest_bufwrite(s, 0xe000000e, "\x20", 0x1);
> +    qtest_bufwrite(s, 0xe000000f, "\x08", 0x1);
> +    qtest_bufwrite(s, 0xe000000b, "\x3d", 0x1);
> +    qtest_bufwrite(s, 0xe000000f, "\x1e", 0x1);
> +
> +    qtest_quit(s);
> +}
> +
>  int main(int argc, char **argv)
>  {
>      const char *arch = qtest_get_arch();
> @@ -60,6 +95,7 @@ int main(int argc, char **argv)
>  
>     if (strcmp(arch, "i386") == 0) {
>          qtest_add_func("fuzz/sdcard/oss_fuzz_29225", oss_fuzz_29225);
> +        qtest_add_func("fuzz/sdcard/oss_fuzz_36217", oss_fuzz_36217);
>     }
>  
>     return g_test_run();
>