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Thomas Gleixner 0b46b4ac92 x86/kaslr: Expose and use the end of the physical memory address space 
commit ea72ce5da2 upstream.

iounmap() on x86 occasionally fails to unmap because the provided valid
ioremap address is not below high_memory. It turned out that this
happens due to KASLR.

KASLR uses the full address space between PAGE_OFFSET and vaddr_end to
randomize the starting points of the direct map, vmalloc and vmemmap
regions.  It thereby limits the size of the direct map by using the
installed memory size plus an extra configurable margin for hot-plug
memory.  This limitation is done to gain more randomization space
because otherwise only the holes between the direct map, vmalloc,
vmemmap and vaddr_end would be usable for randomizing.

The limited direct map size is not exposed to the rest of the kernel, so
the memory hot-plug and resource management related code paths still
operate under the assumption that the available address space can be
determined with MAX_PHYSMEM_BITS.

request_free_mem_region() allocates from (1 << MAX_PHYSMEM_BITS) - 1
downwards.  That means the first allocation happens past the end of the
direct map and if unlucky this address is in the vmalloc space, which
causes high_memory to become greater than VMALLOC_START and consequently
causes iounmap() to fail for valid ioremap addresses.

MAX_PHYSMEM_BITS cannot be changed for that because the randomization
does not align with address bit boundaries and there are other places
which actually require to know the maximum number of address bits.  All
remaining usage sites of MAX_PHYSMEM_BITS have been analyzed and found
to be correct.

Cure this by exposing the end of the direct map via PHYSMEM_END and use
that for the memory hot-plug and resource management related places
instead of relying on MAX_PHYSMEM_BITS. In the KASLR case PHYSMEM_END
maps to a variable which is initialized by the KASLR initialization and
otherwise it is based on MAX_PHYSMEM_BITS as before.

To prevent future hickups add a check into add_pages() to catch callers
trying to add memory above PHYSMEM_END.

Fixes: 0483e1fa6e ("x86/mm: Implement ASLR for kernel memory regions")
Reported-by: Max Ramanouski <max8rr8@gmail.com>
Reported-by: Alistair Popple <apopple@nvidia.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-By: Max Ramanouski <max8rr8@gmail.com>
Tested-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/87ed6soy3z.ffs@tglx
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-09-12 11:11:25 +02:00
arch x86/kaslr: Expose and use the end of the physical memory address space 2024-09-12 11:11:25 +02:00
block block: remove the blk_flush_integrity call in blk_integrity_unregister 2024-09-08 07:54:47 +02:00
certs
crypto crypto: aead,cipher - zeroize key buffer after use 2024-07-11 12:49:04 +02:00
Documentation hwspinlock: Introduce hwspin_lock_bust() 2024-09-08 07:54:43 +02:00
drivers irqchip/gic-v2m: Fix refcount leak in gicv2m_of_init() 2024-09-12 11:11:25 +02:00
fs ksmbd: Unlock on in ksmbd_tcp_set_interfaces() 2024-09-12 11:11:25 +02:00
include x86/kaslr: Expose and use the end of the physical memory address space 2024-09-12 11:11:25 +02:00
init rust: fix the default format for CONFIG_{RUSTC,BINDGEN}_VERSION_TEXT 2024-08-29 17:33:29 +02:00
io_uring io_uring: fix io_match_task must_hold 2024-08-03 08:54:41 +02:00
ipc sysctl: treewide: drop unused argument ctl_table_root::set_ownership(table) 2024-08-11 12:47:13 +02:00
kernel x86/kaslr: Expose and use the end of the physical memory address space 2024-09-12 11:11:25 +02:00
lib sched/topology: Handle NUMA_NO_NODE in sched_numa_find_nth_cpu() 2024-08-29 17:33:24 +02:00
LICENSES
mm x86/kaslr: Expose and use the end of the physical memory address space 2024-09-12 11:11:25 +02:00
net sch/netem: fix use after free in netem_dequeue 2024-09-12 11:11:24 +02:00
rust
samples bpf: Replace bpf_lpm_trie_key 0-length array with flexible array 2024-08-19 06:04:27 +02:00
scripts rust: work around bindgen 0.69.0 issue 2024-08-29 17:33:29 +02:00
security smack: tcp: ipv4, fix incorrect labeling 2024-09-08 07:54:45 +02:00
sound ALSA: hda/realtek: Support mute LED on HP Laptop 14-dq2xxx 2024-09-12 11:11:24 +02:00
tools selftests: mptcp: join: stop transfer when check is done (part 2.2) 2024-09-08 07:54:35 +02:00
usr
virt KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin() 2024-06-27 13:49:11 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes
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Makefile Linux 6.6.50 2024-09-08 07:54:49 +02:00
README

README

Linux kernel

There are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. Please read Documentation/admin-guide/README.rst first.

In order to build the documentation, use make htmldocs or make pdfdocs. The formatted documentation can also be read online at:

https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.