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hw/uefi: clear uefi-vars buffer in uefi_vars_write callback

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When the guest writes to register UEFI_VARS_REG_BUFFER_SIZE, the .write
callback `uefi_vars_write` is invoked. The function allocates a
heap buffer without zeroing the memory, leaving the buffer filled with
residual data from prior allocations. When the guest later reads from
register UEFI_VARS_REG_PIO_BUFFER_TRANSFER, the .read callback
`uefi_vars_read` returns leftover metadata or other sensitive process
memory from the previously allocated buffer, leading to an information
disclosure vulnerability.

Fixes: CVE-2025-8860
Fixes: 90ca4e03c2 ("hw/uefi: add var-service-core.c")
Reported-by: ZDI <zdi-disclosures@trendmicro.com>
Suggested-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Mauro Matteo Cascella <mcascell@redhat.com>
Message-ID: <20250811101128.17661-1-mcascell@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Mauro Matteo Cascella 2025-08-11 12:11:24 +02:00 • committed by Gerd Hoffmann
parent 624d746304
commit f757d9d90d
1 changed files with 2 additions and 2 deletions
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4
hw/uefi/var-service-core.c
View file

@ -259,8 +259,8 @@ static void uefi_vars_write(void *opaque, hwaddr addr, uint64_t val, unsigned si
uv->buf_size = val;
g_free(uv->buffer);
g_free(uv->pio_xfer_buffer);
uv->buffer = g_malloc(uv->buf_size);
uv->pio_xfer_buffer = g_malloc(uv->buf_size);
uv->buffer = g_malloc0(uv->buf_size);
uv->pio_xfer_buffer = g_malloc0(uv->buf_size);
break;
case UEFI_VARS_REG_DMA_BUFFER_ADDR_LO:
uv->buf_addr_lo = val;