Messages in this thread Patch in this message | | | From | Ross Zwisler <> | Subject | [PATCH v7 1/9] dax: fix NULL pointer dereference in __dax_dbg() | Date | Wed, 6 Jan 2016 11:00:55 -0700 |
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__dax_dbg() currently assumes that bh->b_bdev is non-NULL, passing it into bdevname() where is is dereferenced. This assumption isn't always true - when called for reads of holes, ext4_dax_mmap_get_block() returns a buffer head where bh->b_bdev is never set. I hit this BUG while testing the DAX PMD fault path.
Instead, verify that we have a valid bh->b_bdev, else just say "unknown" for the block device.
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Dan Williams <dan.j.williams@intel.com> --- fs/dax.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/fs/dax.c b/fs/dax.c index 7af8797..03cc4a3 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -563,7 +563,12 @@ static void __dax_dbg(struct buffer_head *bh, unsigned long address, { if (bh) { char bname[BDEVNAME_SIZE]; - bdevname(bh->b_bdev, bname); + + if (bh->b_bdev) + bdevname(bh->b_bdev, bname); + else + snprintf(bname, BDEVNAME_SIZE, "unknown"); + pr_debug("%s: %s addr: %lx dev %s state %lx start %lld " "length %zd fallback: %s\n", fn, current->comm, address, bname, bh->b_state, (u64)bh->b_blocknr, -- 2.5.0
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