Revision da094e42848e3c36feaa3b5271e53983fd45424f authored by Prakash Gupta on 18 August 2017, 22:16:21 UTC, committed by Linus Torvalds on 18 August 2017, 22:32:02 UTC
name[] in cma_debugfs_add_one() can only accommodate 16 chars including NULL to store sprintf output. It's common for cma device name to be larger than 15 chars. This can cause stack corrpution. If the gcc stack protector is turned on, this can cause a panic due to stack corruption. Below is one example trace: Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: ffffff8e69a75730 Call trace: dump_backtrace+0x0/0x2c4 show_stack+0x20/0x28 dump_stack+0xb8/0xf4 panic+0x154/0x2b0 print_tainted+0x0/0xc0 cma_debugfs_init+0x274/0x290 do_one_initcall+0x5c/0x168 kernel_init_freeable+0x1c8/0x280 Fix the short sprintf buffer in cma_debugfs_add_one() by using scnprintf() instead of sprintf(). Link: http://lkml.kernel.org/r/1502446217-21840-1-git-send-email-guptap@codeaurora.org Fixes: f318dd083c81 ("cma: Store a name in the cma structure") Signed-off-by: Prakash Gupta <guptap@codeaurora.org> Acked-by: Laura Abbott <labbott@redhat.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Kconfig.debug
config PAGE_EXTENSION
bool "Extend memmap on extra space for more information on page"
---help---
Extend memmap on extra space for more information on page. This
could be used for debugging features that need to insert extra
field for every page. This extension enables us to save memory
by not allocating this extra memory according to boottime
configuration.
config DEBUG_PAGEALLOC
bool "Debug page memory allocations"
depends on DEBUG_KERNEL
depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC && !SPARC
depends on !KMEMCHECK
select PAGE_EXTENSION
select PAGE_POISONING if !ARCH_SUPPORTS_DEBUG_PAGEALLOC
---help---
Unmap pages from the kernel linear mapping after free_pages().
Depending on runtime enablement, this results in a small or large
slowdown, but helps to find certain types of memory corruption.
For architectures which don't enable ARCH_SUPPORTS_DEBUG_PAGEALLOC,
fill the pages with poison patterns after free_pages() and verify
the patterns before alloc_pages(). Additionally,
this option cannot be enabled in combination with hibernation as
that would result in incorrect warnings of memory corruption after
a resume because free pages are not saved to the suspend image.
By default this option will have a small overhead, e.g. by not
allowing the kernel mapping to be backed by large pages on some
architectures. Even bigger overhead comes when the debugging is
enabled by DEBUG_PAGEALLOC_ENABLE_DEFAULT or the debug_pagealloc
command line parameter.
config DEBUG_PAGEALLOC_ENABLE_DEFAULT
bool "Enable debug page memory allocations by default?"
default n
depends on DEBUG_PAGEALLOC
---help---
Enable debug page memory allocations by default? This value
can be overridden by debug_pagealloc=off|on.
config PAGE_POISONING
bool "Poison pages after freeing"
select PAGE_POISONING_NO_SANITY if HIBERNATION
---help---
Fill the pages with poison patterns after free_pages() and verify
the patterns before alloc_pages. The filling of the memory helps
reduce the risk of information leaks from freed data. This does
have a potential performance impact.
Note that "poison" here is not the same thing as the "HWPoison"
for CONFIG_MEMORY_FAILURE. This is software poisoning only.
If unsure, say N
config PAGE_POISONING_NO_SANITY
depends on PAGE_POISONING
bool "Only poison, don't sanity check"
---help---
Skip the sanity checking on alloc, only fill the pages with
poison on free. This reduces some of the overhead of the
poisoning feature.
If you are only interested in sanitization, say Y. Otherwise
say N.
config PAGE_POISONING_ZERO
bool "Use zero for poisoning instead of random data"
depends on PAGE_POISONING
---help---
Instead of using the existing poison value, fill the pages with
zeros. This makes it harder to detect when errors are occurring
due to sanitization but the zeroing at free means that it is
no longer necessary to write zeros when GFP_ZERO is used on
allocation.
If unsure, say N
bool
config DEBUG_PAGE_REF
bool "Enable tracepoint to track down page reference manipulation"
depends on DEBUG_KERNEL
depends on TRACEPOINTS
---help---
This is a feature to add tracepoint for tracking down page reference
manipulation. This tracking is useful to diagnose functional failure
due to migration failures caused by page reference mismatches. Be
careful when enabling this feature because it adds about 30 KB to the
kernel code. However the runtime performance overhead is virtually
nil until the tracepoints are actually enabled.
config DEBUG_RODATA_TEST
bool "Testcase for the marking rodata read-only"
depends on STRICT_KERNEL_RWX
---help---
This option enables a testcase for the setting rodata read-only.
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