From: Hannes Reinecke hare@suse.de

commit 745dfa0d8ec26b24f3304459ff6e9eacc5c8351b upstream.

The ioctl SET_FORCE_LOW_DMA has never worked since the initial git check-in, and the respective setting is nowadays handled correctly. So disable it entirely.

[rientjes@google.com: the SG_SET_FORCE_LOW_DMA ioctl can race with mmap(MAP_POPULATE) or a VM_LOCKED vma to cause a use-after-free which can result in a GPF in practice.]

Signed-off-by: Hannes Reinecke hare@suse.com Reviewed-by: Johannes Thumshirn jthumshirn@suse.de Tested-by: Johannes Thumshirn jthumshirn@suse.de Reviewed-by: Christoph Hellwig hch@lst.de Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: David Rientjes rientjes@google.com --- drivers/scsi/sg.c | 30 +++++++++--------------------- include/scsi/sg.h | 1 - 2 files changed, 9 insertions(+), 22 deletions(-)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -149,7 +149,6 @@ typedef struct sg_fd { /* holds the state of a file descriptor */ struct list_head rq_list; /* head of request list */ struct fasync_struct *async_qp; /* used by asynchronous notification */ Sg_request req_arr[SG_MAX_QUEUE]; /* used as singly-linked list */ - char low_dma; /* as in parent but possibly overridden to 1 */ char force_packid; /* 1 -> pack_id input to read(), 0 -> ignored */ char cmd_q; /* 1 -> allow command queuing, 0 -> don't */ unsigned char next_cmd_len; /* 0: automatic, >0: use on next write() */ @@ -922,24 +921,14 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) /* strange ..., for backward compatibility */ return sfp->timeout_user; case SG_SET_FORCE_LOW_DMA: - result = get_user(val, ip); - if (result) - return result; - if (val) { - sfp->low_dma = 1; - if ((0 == sfp->low_dma) && !sfp->res_in_use) { - val = (int) sfp->reserve.bufflen; - sg_remove_scat(sfp, &sfp->reserve); - sg_build_reserve(sfp, val); - } - } else { - if (atomic_read(&sdp->detaching)) - return -ENODEV; - sfp->low_dma = sdp->device->host->unchecked_isa_dma; - } + /* + * N.B. This ioctl never worked properly, but failed to + * return an error value. So returning '0' to keep compability + * with legacy applications. + */ return 0; case SG_GET_LOW_DMA: - return put_user((int) sfp->low_dma, ip); + return put_user((int) sdp->device->host->unchecked_isa_dma, ip); case SG_GET_SCSI_ID: if (!access_ok(VERIFY_WRITE, p, sizeof (sg_scsi_id_t))) return -EFAULT; @@ -1860,6 +1849,7 @@ sg_build_indirect(Sg_scatter_hold * schp, Sg_fd * sfp, int buff_size) int sg_tablesize = sfp->parentdp->sg_tablesize; int blk_size = buff_size, order; gfp_t gfp_mask = GFP_ATOMIC | __GFP_COMP | __GFP_NOWARN; + struct sg_device *sdp = sfp->parentdp;

if (blk_size < 0) return -EFAULT; @@ -1885,7 +1875,7 @@ sg_build_indirect(Sg_scatter_hold * schp, Sg_fd * sfp, int buff_size) scatter_elem_sz_prev = num; }

- if (sfp->low_dma) + if (sdp->device->host->unchecked_isa_dma) gfp_mask |= GFP_DMA;

if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO)) @@ -2148,8 +2138,6 @@ sg_add_sfp(Sg_device * sdp) sfp->timeout = SG_DEFAULT_TIMEOUT; sfp->timeout_user = SG_DEFAULT_TIMEOUT_USER; sfp->force_packid = SG_DEF_FORCE_PACK_ID; - sfp->low_dma = (SG_DEF_FORCE_LOW_DMA == 0) ? - sdp->device->host->unchecked_isa_dma : 1; sfp->cmd_q = SG_DEF_COMMAND_Q; sfp->keep_orphan = SG_DEF_KEEP_ORPHAN; sfp->parentdp = sdp; @@ -2608,7 +2596,7 @@ static void sg_proc_debug_helper(struct seq_file *s, Sg_device * sdp) jiffies_to_msecs(fp->timeout), fp->reserve.bufflen, (int) fp->reserve.k_use_sg, - (int) fp->low_dma); + (int) sdp->device->host->unchecked_isa_dma); seq_printf(s, " cmd_q=%d f_packid=%d k_orphan=%d closed=0\n", (int) fp->cmd_q, (int) fp->force_packid, (int) fp->keep_orphan); diff --git a/include/scsi/sg.h b/include/scsi/sg.h --- a/include/scsi/sg.h +++ b/include/scsi/sg.h @@ -197,7 +197,6 @@ typedef struct sg_req_info { /* used by SG_GET_REQUEST_TABLE ioctl() */ #define SG_DEFAULT_RETRIES 0

/* Defaults, commented if they differ from original sg driver */ -#define SG_DEF_FORCE_LOW_DMA 0 /* was 1 -> memory below 16MB on i386 */ #define SG_DEF_FORCE_PACK_ID 0 #define SG_DEF_KEEP_ORPHAN 0 #define SG_DEF_RESERVED_SIZE SG_SCATTER_SZ /* load time option */