From: Prasad J Pandit Date: Sat, 9 Jan 2016 01:18:31 +0530 Subject: ide: ahci: reset ncq object to unused on error Bug-Debian: https://bugs.debian.org/810527 When processing NCQ commands, ACHI device emulation prepares a NCQ transfer object; To which an aio control block(aiocb) object is assigned in 'execute_ncq_command'. In case, when the NCQ command is invalid, the 'aiocb' object is not assigned, and NCQ transfer object is left as 'used'. This leads to a use after free kind of error in 'bdrv_aio_cancel_async' via 'ahci_reset_port'. Reset NCQ transfer object to 'unused' to avoid it. Reported-by: Qinghao Tang Signed-off-by: Prasad J Pandit Reviewed-by: John Snow Message-id: 1452282511-4116-1-git-send-email-ppandit@redhat.com Signed-off-by: John Snow --- hw/ide/ahci.c | 1 + 1 file changed, 1 insertion(+) #diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c #index dd1912e..17f1cbd 100644 #--- a/hw/ide/ahci.c #+++ b/hw/ide/ahci.c #@@ -910,6 +910,7 @@ static void ncq_err(NCQTransferState *ncq_tfs) # ide_state->error = ABRT_ERR; # ide_state->status = READY_STAT | ERR_STAT; # ncq_tfs->drive->port_regs.scr_err |= (1 << ncq_tfs->tag); #+ ncq_tfs->used = 0; # } # # static void ncq_finish(NCQTransferState *ncq_tfs) -- Mjt: In 2.1, the code is different. In particular, execute_ncq_command() is part of process_ncq_command(), and there's no ncq_err() function yet. We do the "used = 0" assignment in the exact place where the invalid NCQ command is detected. diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c index 604152a..1d4c60c 100644 --- a/hw/ide/ahci.c +++ b/hw/ide/ahci.c @@ -816,6 +816,7 @@ static void process_ncq_command(AHCIState *s, int port, uint8_t *cmd_fis, default: DPRINTF(port, "error: tried to process non-NCQ command as NCQ\n"); qemu_sglist_destroy(&ncq_tfs->sglist); + ncq_tfs->used = 0; break; } }