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4d5aef3ba9
Before this patch, in zfs_domount, if zfs_root or d_make_root fails, we leave zfsvfs != NULL. This will lead to execution of the error handling `if` statement at the `out` label, and hence to a call to dmu_objset_disown and zfsvfs_free. However, zfs_umount, which we call upon failure of zfs_root and d_make_root already does dmu_objset_disown and zfsvfs_free. I suppose this patch rather adds to the brittleness of this part of the code base, but I don't want to invest more time in this right now. To add a regression test, we'd need some kind of fault injection facility for zfs_root or d_make_root, which doesn't exist right now. And even then, I think that regression test would be too closely tied to the implementation. To repro the double-disown / double-free, do the following: 1. patch zfs_root to always return an error 2. mount a ZFS filesystem Here's the stack trace you would see then: VERIFY3(ds->ds_owner == tag) failed (0000000000000000 == ffff9142361e8000) PANIC at dsl_dataset.c:1003:dsl_dataset_disown() Showing stack for process 28332 CPU: 2 PID: 28332 Comm: zpool Tainted: G O 5.10.103-1.nutanix.el7.x86_64 #1 Call Trace: dump_stack+0x74/0x92 spl_dumpstack+0x29/0x2b [spl] spl_panic+0xd4/0xfc [spl] dsl_dataset_disown+0xe9/0x150 [zfs] dmu_objset_disown+0xd6/0x150 [zfs] zfs_domount+0x17b/0x4b0 [zfs] zpl_mount+0x174/0x220 [zfs] legacy_get_tree+0x2b/0x50 vfs_get_tree+0x2a/0xc0 path_mount+0x2fa/0xa70 do_mount+0x7c/0xa0 __x64_sys_mount+0x8b/0xe0 do_syscall_64+0x38/0x50 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Reviewed-by: Richard Yao <richard.yao@alumni.stonybrook.edu> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Ryan Moeller <ryan@iXsystems.com> Co-authored-by: Christian Schwarz <christian.schwarz@nutanix.com> Signed-off-by: Christian Schwarz <christian.schwarz@nutanix.com> Closes #14025 |
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