linux/init, branch v5.5

mm, debug_pagealloc: don't rely on static keys too early

2020-01-14T02:19:02Z

Commit 96a2b03f281d ("mm, debug_pagelloc: use static keys to enable debugging") has introduced a static key to reduce overhead when debug_pagealloc is compiled in but not enabled. It relied on the assumption that jump_label_init() is called before parse_early_param() as in start_kernel(), so when the "debug_pagealloc=on" option is parsed, it is safe to enable the static key. However, it turns out multiple architectures call parse_early_param() earlier from their setup_arch(). x86 also calls jump_label_init() even earlier, so no issue was found while testing the commit, but same is not true for e.g. ppc64 and s390 where the kernel would not boot with debug_pagealloc=on as found by our QA. To fix this without tricky changes to init code of multiple architectures, this patch partially reverts the static key conversion from 96a2b03f281d. Init-time and non-fastpath calls (such as in arch code) of debug_pagealloc_enabled() will again test a simple bool variable. Fastpath mm code is converted to a new debug_pagealloc_enabled_static() variant that relies on the static key, which is enabled in a well-defined point in mm_init() where it's guaranteed that jump_label_init() has been called, regardless of architecture. [sfr@canb.auug.org.au: export _debug_pagealloc_enabled_early] Link: http://lkml.kernel.org/r/20200106164944.063ac07b@canb.auug.org.au Link: http://lkml.kernel.org/r/20191219130612.23171-1-vbabka@suse.cz Fixes: 96a2b03f281d ("mm, debug_pagelloc: use static keys to enable debugging") Signed-off-by: Vlastimil Babka Signed-off-by: Stephen Rothwell Cc: Joonsoo Kim Cc: "Kirill A. Shutemov" Cc: Michal Hocko Cc: Vlastimil Babka Cc: Matthew Wilcox Cc: Mel Gorman Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Qian Cai Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Revert "fs: remove ksys_dup()"

2020-01-03T00:15:33Z

This reverts commit 8243186f0cc7 ("fs: remove ksys_dup()") and the subsequent fix for it in commit 2d3145f8d280 ("early init: fix error handling when opening /dev/console"). Trying to use filp_open() and f_dupfd() instead of pseudo-syscalls caused more trouble than what is worth it: it requires accessing vfs internals and it turns out there were other bugs in it too. In particular, the file reference counting was wrong - because unlike the original "open+2*dup" sequence it used "filp_open+3*f_dupfd" and thus had an extra leaked file reference. That in turn then caused odd problems with Androidx86 long after boot becaue of how the extra reference to the console kept the session active even after all file descriptors had been closed. Reported-by: youling 257 Cc: Arvind Sankar Cc: Al Viro Signed-off-by: Dominik Brodowski Signed-off-by: Linus Torvalds

early init: fix error handling when opening /dev/console

2019-12-17T21:10:11Z

The comment says "this should never fail", but it definitely can fail when you have odd initial boot filesystems, or kernel configurations. So get the error handling right: filp_open() returns an error pointer. Reported-by: Jesse Barnes Reported-by: youling 257 Fixes: 8243186f0cc7 ("fs: remove ksys_dup()") Cc: Dominik Brodowski Signed-off-by: Linus Torvalds

Fix root mounting with no mount options

2019-12-16T16:42:39Z

The "trivial conversion" in commit cccaa5e33525 ("init: use do_mount() instead of ksys_mount()") was totally broken, since it didn't handle the case of a NULL mount data pointer. And while I had "tested" it (and presumably Dominik had too) that bug was hidden by me having options. Cc: Dominik Brodowski Cc: Arnd Bergmann Reported-by: Ondřej Jirman Reported-by: Guenter Roeck Reported-by: Naresh Kamboju Reported-and-tested-by: Borislav Petkov Tested-by: Chris Clayton Tested-by: Eric Biggers Tested-by: Geert Uytterhoeven Tested-by: Guido Günther Signed-off-by: Linus Torvalds

fs: remove ksys_dup()

2019-12-12T18:00:36Z

ksys_dup() is used only at one place in the kernel, namely to duplicate fd 0 of /dev/console to stdout and stderr. The same functionality can be achieved by using functions already available within the kernel namespace. Signed-off-by: Dominik Brodowski

init: unify opening /dev/console as stdin/stdout/stderr

2019-12-12T17:58:24Z

Merge the two instances where /dev/console is opened as stdin/stdout/stderr. Signed-off-by: Dominik Brodowski

init: use do_mount() instead of ksys_mount()

2019-12-12T13:50:05Z

In prepare_namespace(), do_mount() can be used instead of ksys_mount() as the first and third argument are const strings in the kernel, the second and fourth argument are passed through anyway, and the fifth argument is NULL. In do_mount_root(), ksys_mount() is called with the first and third argument being already kernelspace strings, which do not need to be copied over from userspace to kernelspace (again). The second and fourth arguments are passed through to do_mount() anyway. The fifth argument, while already residing in kernelspace, needs to be put into a page of its own. Then, do_mount() can be used instead of ksys_mount(). Once this is done, there are no in-kernel users to ksys_mount() left, which can therefore be removed. Signed-off-by: Dominik Brodowski

initrd: use do_mount() instead of ksys_mount()

2019-12-12T13:50:03Z

All three calls to ksys_mount() in initrd-related kernel code can be switched over to do_mount(): - the first and third arguments are const strings in the kernel, and do not need to be copied over from userspace; - the fifth argument is NULL, and therefore no page needs to be, copied over from userspace; - the second and fourth argument are passed through anyway. Signed-off-by: Dominik Brodowski

devtmpfs: use do_mount() instead of ksys_mount()

2019-12-12T13:49:57Z

In devtmpfs, do_mount() can be called directly instead of complex wrapping by ksys_mount(): - the first and third arguments are const strings in the kernel, and do not need to be copied over from userspace; - the fifth argument is NULL, and therefore no page needs to be copied over from userspace; - the second and fourth argument are passed through anyway. Signed-off-by: Dominik Brodowski

init/Kconfig: fix indentation

2019-12-05T03:44:13Z

Adjust indentation from spaces to tab (+optional two spaces) as in coding style with command like: $ sed -e 's/^ / /' -i */Kconfig Link: http://lkml.kernel.org/r/1574306670-30234-1-git-send-email-krzk@kernel.org Signed-off-by: Krzysztof Kozlowski Cc: Jiri Kosina Cc: Masahiro Yamada Cc: Greg Kroah-Hartman Cc: David Hildenbrand Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds