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

um: Fix out-of-bounds read in LDT setup

syscall_stub_data() expects the data_count parameter to be the number of longs, not bytes.

================================================================== BUG: KASAN: stack-out-of-bounds in syscall_stub_data+0x70/0xe0 Read of size 128 at addr 000000006411f6f0 by task swapper/1

CPU: 0 PID: 1 Comm: swapper Not tainted 5.18.0+ #18 Call Trace: show_stack.cold+0x166/0x2a7 __dump_stack+0x3a/0x43 dump_stack_lvl+0x1f/0x27 print_report.cold+0xdb/0xf81 kasan_report+0x119/0x1f0 kasan_check_range+0x3a3/0x440 memcpy+0x52/0x140 syscall_stub_data+0x70/0xe0 write_ldt_entry+0xac/0x190 init_new_ldt+0x515/0x960 init_new_context+0x2c4/0x4d0 mm_init.constprop.0+0x5ed/0x760 mm_alloc+0x118/0x170 0x60033f48 do_one_initcall+0x1d7/0x860 0x60003e7b kernel_init+0x6e/0x3d4 new_thread_handler+0x1e7/0x2c0

The buggy address belongs to stack of task swapper/1 and is located at offset 64 in frame: init_new_ldt+0x0/0x960

This frame has 2 objects: [32, 40) addr [64, 80) desc

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/10995a382271254bd276627ec74136da4a23c4a6
• https://git.kernel.org/stable/c/24ca648bf5f72ed8878cf09b5d4431935779681e
• https://git.kernel.org/stable/c/2a4a62a14be1947fa945c5c11ebf67326381a568
• https://git.kernel.org/stable/c/3549ab4b962cf619e8c55484a0d870a34b3f845f
• https://git.kernel.org/stable/c/668ca34a428d6ffc0f99a1a6a9b661a288d4183b
• https://git.kernel.org/stable/c/91e5ba2af2d729d5126aefd5aa3eadc69b8426e5
• https://git.kernel.org/stable/c/9caad70819aef3431abaf73ba5163b55b161aba0
• https://git.kernel.org/stable/c/cf0dabc37446c5ee538ae7b4c467ab0e53fa5463
• https://git.kernel.org/stable/c/ef1dc929a1e5fa1b2d842256db9fb8710d3be910