831b624df1
persistent_ram_vmap() returns the page start vaddr.
persistent_ram_iomap() supports non-page-aligned mapping.
persistent_ram_buffer_map() always adds offset-in-page to the vaddr
returned from these two functions, which causes incorrect mapping of
non-page-aligned persistent ram buffer.
By default ftrace_size is 4096 and max_ftrace_cnt is nr_cpu_ids. Without
this patch, the zone_sz in ramoops_init_przs() is 4096/nr_cpu_ids which
might not be page aligned. If the offset-in-page > 2048, the vaddr will be
in next page. If the next page is not mapped, it will cause kernel panic:
[ 0.074231] BUG: unable to handle kernel paging request at ffffa19e0081b000
...
[ 0.075000] RIP: 0010:persistent_ram_new+0x1f8/0x39f
...
[ 0.075000] Call Trace:
[ 0.075000] ramoops_init_przs.part.10.constprop.15+0x105/0x260
[ 0.075000] ramoops_probe+0x232/0x3a0
[ 0.075000] platform_drv_probe+0x3e/0xa0
[ 0.075000] driver_probe_device+0x2cd/0x400
[ 0.075000] __driver_attach+0xe4/0x110
[ 0.075000] ? driver_probe_device+0x400/0x400
[ 0.075000] bus_for_each_dev+0x70/0xa0
[ 0.075000] driver_attach+0x1e/0x20
[ 0.075000] bus_add_driver+0x159/0x230
[ 0.075000] ? do_early_param+0x95/0x95
[ 0.075000] driver_register+0x70/0xc0
[ 0.075000] ? init_pstore_fs+0x4d/0x4d
[ 0.075000] __platform_driver_register+0x36/0x40
[ 0.075000] ramoops_init+0x12f/0x131
[ 0.075000] do_one_initcall+0x4d/0x12c
[ 0.075000] ? do_early_param+0x95/0x95
[ 0.075000] kernel_init_freeable+0x19b/0x222
[ 0.075000] ? rest_init+0xbb/0xbb
[ 0.075000] kernel_init+0xe/0xfc
[ 0.075000] ret_from_fork+0x3a/0x50
Signed-off-by: Bin Yang <bin.yang@intel.com>
[kees: add comments describing the mapping differences, updated commit log]
Fixes: 24c3d2f342ed ("staging: android: persistent_ram: Make it possible to use memory outside of bootmem")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.