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Chunwei Chen
6c9b4f18d3
In dbuf_sync_leaf, we clone the arc_buf in dr if we share it with db
except for overridden case. However, this exception causes a race where
dbuf_new_size could free the arc_buf after the last dereference of
*datap and causes use-after-free. We fix this by cloning the buf
regardless if it's overridden.
The race:
--
P0 P1
dbuf_hold_impl()
// dbuf_hold_copy passed
// because db_data_pending NULL
dbuf_sync_leaf()
// doesn't clone *datap
// *datap derefed to db_buf
dbuf_write(*datap)
dbuf_new_size()
dmu_buf_will_dirty()
dbuf_fix_old_data()
// alloc new buf for P0 dr
// but can't change *datap
arc_alloc_buf()
arc_buf_destroy()
// alloc new buf for db_buf
// and destroy old buf
dbuf_write() // continue
abd_get_from_buf(data->b_data,
arc_buf_size(data))
// use-after-free
--
Here's an example when it happens:
BUG: kernel NULL pointer dereference, address: 000000000000002e
RIP: 0010:arc_buf_size+0x1c/0x30 [zfs]
Call Trace:
dbuf_write+0x3ff/0x580 [zfs]
dbuf_sync_leaf+0x13c/0x530 [zfs]
dbuf_sync_list+0xbf/0x120 [zfs]
dnode_sync+0x3ea/0x7a0 [zfs]
sync_dnodes_task+0x71/0xa0 [zfs]
taskq_thread+0x2b8/0x4e0 [spl]
kthread+0x112/0x130
ret_from_fork+0x1f/0x30
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Chunwei Chen <david.chen@nutanix.com>
Co-authored-by: Chunwei Chen <david.chen@nutanix.com>
Closes #16854
OpenZFS is an advanced file system and volume manager which was originally developed for Solaris and is now maintained by the OpenZFS community. This repository contains the code for running OpenZFS on Linux and FreeBSD.
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Full documentation for installing OpenZFS on your favorite operating system can be found at the Getting Started Page.
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We have a separate document with contribution guidelines.
We have a Code of Conduct.
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OpenZFS is released under a CDDL license.
For more details see the NOTICE, LICENSE and COPYRIGHT files; UCRL-CODE-235197
Supported Kernels
- The
METAfile contains the officially recognized supported Linux kernel versions. - Supported FreeBSD versions are any supported branches and releases starting from 13.0-RELEASE.