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a2cb8818a3
commit 28aa29986dde79e8466bc87569141291053833f5 upstream.
When the PAGEMAP_SCAN ioctl is invoked with vec_len = 0 reaches
pagemap_scan_backout_range(), kernel panics with null-ptr-deref:
[ 44.936808] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI
[ 44.937797] KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
[ 44.938391] CPU: 1 UID: 0 PID: 2480 Comm: reproducer Not tainted 6.17.0-rc6 #22 PREEMPT(none)
[ 44.939062] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[ 44.939935] RIP: 0010:pagemap_scan_thp_entry.isra.0+0x741/0xa80
<snip registers, unreliable trace>
[ 44.946828] Call Trace:
[ 44.947030] <TASK>
[ 44.949219] pagemap_scan_pmd_entry+0xec/0xfa0
[ 44.952593] walk_pmd_range.isra.0+0x302/0x910
[ 44.954069] walk_pud_range.isra.0+0x419/0x790
[ 44.954427] walk_p4d_range+0x41e/0x620
[ 44.954743] walk_pgd_range+0x31e/0x630
[ 44.955057] __walk_page_range+0x160/0x670
[ 44.956883] walk_page_range_mm+0x408/0x980
[ 44.958677] walk_page_range+0x66/0x90
[ 44.958984] do_pagemap_scan+0x28d/0x9c0
[ 44.961833] do_pagemap_cmd+0x59/0x80
[ 44.962484] __x64_sys_ioctl+0x18d/0x210
[ 44.962804] do_syscall_64+0x5b/0x290
[ 44.963111] entry_SYSCALL_64_after_hwframe+0x76/0x7e
vec_len = 0 in pagemap_scan_init_bounce_buffer() means no buffers are
allocated and p->vec_buf remains set to NULL.
This breaks an assumption made later in pagemap_scan_backout_range(), that
page_region is always allocated for p->vec_buf_index.
Fix it by explicitly checking p->vec_buf for NULL before dereferencing.
Other sites that might run into same deref-issue are already (directly or
transitively) protected by checking p->vec_buf.
Note:
From PAGEMAP_SCAN man page, it seems vec_len = 0 is valid when no output
is requested and it's only the side effects caller is interested in,
hence it passes check in pagemap_scan_get_args().
This issue was found by syzkaller.
Link: https://lkml.kernel.org/r/20250922082206.6889-1-acsjakub@amazon.de
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .pylintrc | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| 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 reStructuredText 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.