Description
In the Linux kernel, the following vulnerability has been resolved: dcache: Limit the minimal number of bucket to two There is an OOB read problem on dentry_hashtable when user sets 'dhash_entries=1': BUG: unable to handle page fault for address: ffff888b30b774b0 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page Oops: Oops: 0000 [#1] SMP PTI RIP: 0010:__d_lookup+0x56/0x120 Call Trace: d_lookup.cold+0x16/0x5d lookup_dcache+0x27/0xf0 lookup_one_qstr_excl+0x2a/0x180 start_dirop+0x55/0xa0 simple_start_creating+0x8d/0xa0 debugfs_start_creating+0x8c/0x180 debugfs_create_dir+0x1d/0x1c0 pinctrl_init+0x6d/0x140 do_one_initcall+0x6d/0x3d0 kernel_init_freeable+0x39f/0x460 kernel_init+0x2a/0x260 There will be only one bucket in dentry_hashtable when dhash_entries is set as one, and d_hash_shift is calculated as 32 by dcache_init(). Then, following process will access more than one buckets(which memory region is not allocated) in dentry_hashtable: d_lookup b = d_hash(hash) dentry_hashtable + ((u32)hashlen >> d_hash_shift) // The C standard defines the behavior of right shift amounts // exceeding the bit width of the operand as undefined. The // result of '(u32)hashlen >> d_hash_shift' becomes 'hashlen', // so 'b' will point to an unallocated memory region. hlist_bl_for_each_entry_rcu(b) hlist_bl_first_rcu(head) h->first // read OOB! Fix it by limiting the minimal number of dentry_hashtable bucket to two, so that 'd_hash_shift' won't exceeds the bit width of type u32.
Product status
99d263d4c5b2f541dfacb5391e22e8c91ea982a6 (git) before 426ef05e82ee52c8d0e95fc0808b7383d8352d73
99d263d4c5b2f541dfacb5391e22e8c91ea982a6 (git) before ddd57ebce245f9c7e2f6902a6c087d6186d2385d
99d263d4c5b2f541dfacb5391e22e8c91ea982a6 (git) before 755b40903eff563768d4d96fd4ef51ec48adde3b
99d263d4c5b2f541dfacb5391e22e8c91ea982a6 (git) before 5718df131ab78897a9dd1f2e71c3ba732d4392af
99d263d4c5b2f541dfacb5391e22e8c91ea982a6 (git) before 277cedabb0ab86baae83fa58218be13c6d3e5526
99d263d4c5b2f541dfacb5391e22e8c91ea982a6 (git) before f08fe8891c3eeb63b73f9f1f6d97aa629c821579
d4c96061fddd129778ce8b70fb093aa532f422d0 (git)
be2378cbffe50ce0161f0fdee914adee98af53dc (git)
a8be8af18485f9fade90e1743d940252a39eec84 (git)
b5cf3193759f7cd1cfbeef11f5cf067bbce22e55 (git)
3.17
Any version before 3.17
6.6.136 (semver)
6.12.83 (semver)
6.18.24 (semver)
6.19.14 (semver)
7.0.1 (semver)
7.1-rc1 (original_commit_for_fix)
References
git.kernel.org/...c/426ef05e82ee52c8d0e95fc0808b7383d8352d73
git.kernel.org/...c/ddd57ebce245f9c7e2f6902a6c087d6186d2385d
git.kernel.org/...c/755b40903eff563768d4d96fd4ef51ec48adde3b
git.kernel.org/...c/5718df131ab78897a9dd1f2e71c3ba732d4392af
git.kernel.org/...c/277cedabb0ab86baae83fa58218be13c6d3e5526
git.kernel.org/...c/f08fe8891c3eeb63b73f9f1f6d97aa629c821579