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sg_write()/bsg_write() is not fit to be called under KERNEL_DS

Both damn things interpret userland pointers embedded into the payload;
worse, they are actually traversing those.  Leaving aside the bad
API design, this is very much _not_ safe to call with KERNEL_DS.
Bail out early if that happens.

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Al Viro
Al Viro committed Dec 16, 2016
1 parent f698ccc commit 128394eff343fc6d2f32172f03e24829539c5835
Showing with 6 additions and 0 deletions.
  1. +3 −0 block/bsg.c
  2. +3 −0 drivers/scsi/sg.c
@@ -655,6 +655,9 @@ bsg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)

dprintk("%s: write %Zd bytes\n", bd->name, count);

if (unlikely(segment_eq(get_fs(), KERNEL_DS)))
return -EINVAL;

bsg_set_block(bd, file);

bytes_written = 0;
@@ -581,6 +581,9 @@ sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos)
sg_io_hdr_t *hp;
unsigned char cmnd[SG_MAX_CDB_SIZE];

if (unlikely(segment_eq(get_fs(), KERNEL_DS)))
return -EINVAL;

if ((!(sfp = (Sg_fd *) filp->private_data)) || (!(sdp = sfp->parentdp)))
return -ENXIO;
SCSI_LOG_TIMEOUT(3, sg_printk(KERN_INFO, sdp,

1 comment on commit 128394e

@xiagw

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commented on 128394e Dec 23, 2017

bingo

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