Fix panic : free a NULL point in dmu_send_impl #4969
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Reference issue: [93344.134598] [<ffffffff8130fa9d>] dump_stack+0x4d/0x63 [93344.134603] [<ffffffffa0d10f13>] spl_dumpstack+0x3d/0x3f [spl] [93344.134605] [<ffffffffa0d110cb>] spl_panic+0xa9/0xdc [spl] [93344.134608] [<ffffffffa0d10593>] ? vn_rdwr+0x159/0x1b3 [spl] [93344.134611] [<ffffffff814d0a10>] ? mutex_unlock+0x9/0xb [93344.134628] [<ffffffffa0dddff9>] ? dump_bytes_cb+0x10f/0x123 [zfs] [93344.134630] [<ffffffffa0d0a412>] spl_kmem_free+0x44/0xbf [spl] [93344.134633] [<ffffffffa0d3b6ec>] fnvlist_pack_free+0x9/0xb [znvpair] [93344.134644] [<ffffffffa0ddf884>] dmu_send_impl+0x529/0x120a [zfs] [93344.134645] [<ffffffff814d0a10>] ? mutex_unlock+0x9/0xb [93344.134657] [<ffffffffa0de06fc>] dmu_send_obj+0x197/0x1bc [zfs] [93344.134669] [<ffffffffa0e5aa52>] zfs_ioc_send+0x1f7/0x236 [zfs] [93344.134682] [<ffffffffa0e60a63>] zfsdev_ioctl+0x40e/0x521 [zfs] [93344.134684] [<ffffffff81059337>] ? check_preempt_curr+0x3e/0x6c [93344.134686] [<ffffffff810fc891>] do_vfs_ioctl+0x3f5/0x43d [93344.134688] [<ffffffff8103fd2e>] ? _do_fork+0x229/0x24e [93344.134689] [<ffffffff810368d2>] ? __do_page_fault+0x24e/0x367 [93344.134691] [<ffffffff810fc912>] SyS_ioctl+0x39/0x61 [93344.134692] [<ffffffff814d2317>] entry_SYSCALL_64_fastpath+0x12/0x6a Analysis: If the send stream isn't resume from specified object and offset, we come to dmu_send_impl() with zero input of resumeobj and resumeoff. In other words, the address of buffer payload will stay NULL, we shouldn't free it in this situation. Solution: Examine the buf len of payload before we decide to free it.
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Closing, addressed in the spl. |
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Reference issue: ##4967
This issue maybe introduced by commit #47dfff3
[93344.134598] [] dump_stack+0x4d/0x63
[93344.134603] [] spl_dumpstack+0x3d/0x3f [spl]
[93344.134605] [] spl_panic+0xa9/0xdc [spl]
[93344.134608] [] ? vn_rdwr+0x159/0x1b3 [spl]
[93344.134611] [] ? mutex_unlock+0x9/0xb
[93344.134628] [] ? dump_bytes_cb+0x10f/0x123 [zfs]
[93344.134630] [] spl_kmem_free+0x44/0xbf [spl]
[93344.134633] [] fnvlist_pack_free+0x9/0xb [znvpair]
[93344.134644] [] dmu_send_impl+0x529/0x120a [zfs]
[93344.134645] [] ? mutex_unlock+0x9/0xb
[93344.134657] [] dmu_send_obj+0x197/0x1bc [zfs]
[93344.134669] [] zfs_ioc_send+0x1f7/0x236 [zfs]
[93344.134682] [] zfsdev_ioctl+0x40e/0x521 [zfs]
[93344.134684] [] ? check_preempt_curr+0x3e/0x6c
[93344.134686] [] do_vfs_ioctl+0x3f5/0x43d
[93344.134688] [] ? _do_fork+0x229/0x24e
[93344.134689] [] ? __do_page_fault+0x24e/0x367
[93344.134691] [] SyS_ioctl+0x39/0x61
[93344.134692] [] entry_SYSCALL_64_fastpath+0x12/0x6a
Analysis:
If the send stream isn't resume from specified object and offset, we come to dmu_send_impl() with zero input of resumeobj and resumeoff, which means we will not initialize the buffer of payload.
In other words, the address of buffer payload will stay NULL, we shouldn't free it in this situation.
Solution:
Examine the buf len of payload before we decide to free it.