CVE-2022-50497

In the Linux kernel, the following vulnerability has been resolved:

binfmt_misc: fix shift-out-of-bounds in check_special_flags

UBSAN reported a shift-out-of-bounds warning:

left shift of 1 by 31 places cannot be represented in type int Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x8d/0xcf lib/dump_stack.c:106 ubsan_epilogue+0xa/0x44 lib/ubsan.c:151 __ubsan_handle_shift_out_of_bounds+0x1e7/0x208 lib/ubsan.c:322 check_special_flags fs/binfmt_misc.c:241 [inline] create_entry fs/binfmt_misc.c:456 [inline] bm_register_write+0x9d3/0xa20 fs/binfmt_misc.c:654 vfs_write+0x11e/0x580 fs/read_write.c:582 ksys_write+0xcf/0x120 fs/read_write.c:637 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x34/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x4194e1

Since the type of Nodes flags is unsigned long, we should define these macros with same type too.

Weakness

The product reads data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
• When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
• Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
• To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/540.html

References

• https://git.kernel.org/stable/c/0f1a48994b3e516d5c7fd5d12204fdba7a604771
• https://git.kernel.org/stable/c/419b808504c26b3e3342365f34ccd0843e09a7f8
• https://git.kernel.org/stable/c/6a46bf558803dd2b959ca7435a5c143efe837217
• https://git.kernel.org/stable/c/88cea1676a09f7c45a1438153a126610c33b1590
• https://git.kernel.org/stable/c/97382a2639b1cd9631f6069061e9d7062cd2b098
• https://git.kernel.org/stable/c/a651bb5ff997b9f02662bcdef3d8b4e6f0d79656
• https://git.kernel.org/stable/c/a91123d4bda463469f68f0427adabf8108001f94
• https://git.kernel.org/stable/c/dcbc51d31d0afbd45e830e3cf565a7b3ca7bf0d8
• https://git.kernel.org/stable/c/ea6145370be8016755c43aca799815fc4b8c88b1