d04adc383f
commit f7d63b50898172b9eb061b9e2daad61b428792d0 upstream.
[ Upstream commit 49beadbd47c270a00754c107a837b4f29df4c822 ]
While the concept of checking for dangling pointers to local variables
at function exit is really interesting, the gcc-12 implementation is not
compatible with reality, and results in false positives.
For example, gcc sees us putting things on a local list head allocated
on the stack, which involves exactly those kinds of pointers to the
local stack entry:
In function ‘__list_add’,
inlined from ‘list_add_tail’ at include/linux/list.h:102:2,
inlined from ‘rebuild_snap_realms’ at fs/ceph/snap.c:434:2:
include/linux/list.h:74:19: warning: storing the address of local variable ‘realm_queue’ in ‘*&realm_27(D)->rebuild_item.prev’ [-Wdangling-pointer=]
74 | new->prev = prev;
| ~~~~~~~~~~^~~~~~
But then gcc - understandably - doesn't really understand the big
picture how the doubly linked list works, so doesn't see how we then end
up emptying said list head in a loop and the pointer we added has been
removed.
Gcc also complains about us (intentionally) using this as a way to store
a kind of fake stack trace, eg
drivers/acpi/acpica/utdebug.c:40:38: warning: storing the address of local variable ‘current_sp’ in ‘acpi_gbl_entry_stack_pointer’ [-Wdangling-pointer=]
40 | acpi_gbl_entry_stack_pointer = ¤t_sp;
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~
which is entirely reasonable from a compiler standpoint, and we may want
to change those kinds of patterns, but not not.
So this is one of those "it would be lovely if the compiler were to
complain about us leaving dangling pointers to the stack", but not this
way.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.
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.