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[SCSI] st: fix possible memory use after free after MTSETBLK ioctl 

A memory use after free bug can manifest if the MTSETBLK or SET_DENS_AND_BLK
ioctl features are used to set the tape's blocksize from 0 to non-zero.
After the driver sets the new block size, in this one case it calls
normalize_buffer() to free the device's internal data buffers.  However, the
ioctl code assumes there is always a buffer and does not check or allocate
a buffer if there isn't one.  So any following ioctl calls can corrupt
a part of memory by writing data to memory that the st driver had freed.

This patch removes the normalize_buffer() call and the specialness of
changing from a 0 to non-zero blocksize to fix the possible use of
memory after it has been freed by the st driver.

signed-off-by: David Jeffery <djeffery@redhat.com>
Acked-by: Kai Makisara <kai.makisara@kolumbus.fi>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>
This commit is contained in:
David Jeffery 2009-09-28 13:54:24 -04:00 committed by James Bottomley
parent 2afc95bf54
commit 2c2ed8bfd8
1 changed files with 0 additions and 3 deletions
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3
drivers/scsi/st.c
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@ -2859,11 +2859,8 @@ static int st_int_ioctl(struct scsi_tape *STp, unsigned int cmd_in, unsigned lon
ioctl_result = st_int_ioctl(STp, MTBSF, 1);
if (cmd_in == MTSETBLK || cmd_in == SET_DENS_AND_BLK) {
int old_block_size = STp->block_size;
STp->block_size = arg & MT_ST_BLKSIZE_MASK;
if (STp->block_size != 0) {
if (old_block_size == 0)
normalize_buffer(STp->buffer);
(STp->buffer)->buffer_blocks =
(STp->buffer)->buffer_size / STp->block_size;
}