Re: [PATCH v2 000/101] fbdev: Fix memory leak in option parsing
From: Helge Deller
Date: Mon Mar 20 2023 - 15:33:12 EST
Hi Thomas,
On 3/20/23 11:07, Thomas Zimmermann wrote:
Geert, Helge? Do you have further comments? There's not really much for a v3 yet.
I understand the motivation and I see you invested a lot of work on it,
which is really appreciated.
But I have mixed feelings about that patch itself.
Nevertheless, it mixes multiple things.
Regarding the possible memory leak (for the parameter) you added in various
places a kfree(), but this doesn't make it easier for the driver author to know
when to free and when not.
I wonder if it would be possible to store the kstrdup() value in the
"struct module" (or somewhere module related) instead add kfree it at a central place when the
module is unloaded (instead inside the driver itself). That way no driver needs
to be touched and there are less changes necessary.
And it would change it back to globally-owned strings.
With such a change I think the new command parsing functions wouldn't be needed
either, and ideally, where possible, a conversion to module_param() in various
places would be better.
I'm sure I haven't overlooked everything yet, but I think if we can reduce
the necessary changes by fixing things globally it makes more sense.
Helge
Best regards
Thomas
Am 09.03.23 um 17:00 schrieb Thomas Zimmermann:
Introduce struct option_iter and helpers to parse command-line
options with comma-separated key-value pairs. Then convert fbdev
drivers to the new interface. Fixes a memory leak in the parsing of
the video= option.
Before commit 73ce73c30ba9 ("fbdev: Transfer video= option strings to
caller; clarify ownership"), a call to fb_get_options() either
returned an internal string or a duplicated string; hence ownership of
the string's memory buffer was not well defined, but depended on how
users specified the video= option on the kernel command line. For
global settings, the caller owned the returned memory and for per-driver
settings, fb_get_options() owned the memory. As calling drivers were
unable to detect the case, they had no option but to leak the the memory.
Commit 73ce73c30ba9 ("fbdev: Transfer video= option strings to caller;
clarify ownership") changed semantics to caller-owned strings. Drivers
still leaked the memory, but at least ownership was clear.
This patchset fixes the memory leak and changes string ownership back
to fb_get_options(). Patch 1 introduces struct option_iter and a few
helpers. The interface takes an option string, such as video=, in the
common form value1,key2:value2,value3 etc and returns the individual
comma-separated pairs. Various modules use this pattern, so the code
is located under lib/.
Patches 2 to 100 go through fbdev drivers and convert them to the new
interface. This often requires a number of cleanups. A driver would
typically refer to the option string's video mode. Such strings are now
copied to driver-allocated memory so that drivers don't refer directly
to the option string's memory. The option iterator then replaces manual
parsing loops based on strsep(","). All driver-allocated memory is
released by removing the device or unloading the module.
Patch 101 finally changes the ownership of the option string to be
internal to fb_get_option(); thereby fixing the memory leak. The option
iterator holds its own copy of the string and is not affected by the
change.
Most fbdev drivers only support to parse option strings if they are
built-in. I assume that's because of the original fuzzy semantics of
fb_get_options(). A later patchset could change the driver to respect
video= settings in any configuration.
v2:
* use kstrdup()/kfree() for video strings (Geert, Timur)
* fix iterator docs (Randy)
* update iterator interface
Thomas Zimmermann (101):
lib: Add option iterator
fbdev/68328fb: Remove trailing whitespaces
fbdev/68328fb: Remove unused option string
fbdev/acornfb: Only init fb_info once
fbdev/acornfb: Parse option string with struct option_iter
fbdev/amifb: Duplicate video-mode option string
fbdev/amifb: Parse option string with struct option_iter
fbdev/arkfb: Duplicate video-mode option string
fbdev/atafb: Duplicate video-mode option string
fbdev/atafb: Parse option string with struct option_iter
fbdev/aty: Duplicate video-mode option string
fbdev/aty: Parse option string with struct option_iter
fbdev/au1100fb: Parse option string with struct option_iter
fbdev/au1200fb: Parse option string with struct option_iter
fbdev/cirrusfb: Duplicate video-mode option string
fbdev/cirrusfb: Parse option string with struct option_iter
fbdev/controlfb: Remove trailing whitespaces
fbdev/controlfb: Parse option string with struct option_iter
fbdev/cyber2000fb: Parse option string with struct option_iter
fbdev/efifb: Parse option string with struct option_iter
fbdev/fm2fb: Parse option string with struct option_iter
fbdev/fsl-diu-fb: Duplicate video-mode option string
fbdev/fsl-diu-fb: Parse option string with struct option_iter
fbdev/gbefb: Duplicate video-mode option string
fbdev/gbefb: Parse option string with struct option_iter
fbdev/geode: Duplicate video-mode option string
fbdev/geode: Parse option string with struct option_iter
fbdev/grvga: Duplicate video-mode option string
fbdev/grvga: Parse option string with struct option_iter
fbdev/gxt4500: Duplicate video-mode option string
fbdev/hyperv_fb: Duplicate video-mode option string
fbdev/i740fb: Duplicate video-mode option string
fbdev/i740fb: Parse option string with struct option_iter
fbdev/i810: Duplicate video-mode option string
fbdev/i810: Parse option string with struct option_iter
fbdev/imsttfb: Parse option string with struct option_iter
fbdev/intelfb: Duplicate video-mode option string
fbdev/intelfb: Parse option string with struct option_iter
fbdev/imxfb: Duplicate video-mode option string
fbdev/imxfb: Parse option string with struct option_iter
fbdev/kyrofb: Duplicate video-mode option string
fbdev/kyrofb: Parse option string with struct option_iter
fbdev/macfb: Remove trailing whitespaces
fbdev/macfb: Parse option string with struct option_iter
fbdev/matroxfb: Parse option string with struct option_iter
fbdev/mx3fb: Duplicate video-mode option string
fbdev/mx3fb: Parse option string with struct option_iter
fbdev/neofb: Duplicate video-mode option string
fbdev/neofb: Parse option string with struct option_iter
fbdev/nvidiafb: Duplicate video-mode option string
fbdev/nvidiafb: Parse option string with struct option_iter
fbdev/ocfb: Duplicate video-mode option string
fbdev/ocfb: Parse option string with struct option_iter
fbdev/omapfb: Parse option string with struct option_iter
fbdev/platinumfb: Remove trailing whitespaces
fbdev/platinumfb: Parse option string with struct option_iter
fbdev/pm2fb: Duplicate video-mode option string
fbdev/pm2fb: Parse option string with struct option_iter
fbdev/pm3fb: Duplicate video-mode option string
fbdev/pm3fb: Parse option string with struct option_iter
fbdev/ps3fb: Duplicate video-mode option string
fbdev/ps3fb: Parse option string with struct option_iter
fbdev/pvr2fb: Duplicate video-mode option string
fbdev/pvr2fb: Parse option string with struct option_iter
fbdev/pxafb: Parse option string with struct option_iter
fbdev/rivafb: Duplicate video-mode option string
fbdev/rivafb: Parse option string with struct option_iter
fbdev/s3fb: Duplicate video-mode option string
fbdev/s3fb: Parse option string with struct option_iter
fbdev/savagefb: Duplicate video-mode option string
fbdev/savagefb: Parse option string with struct option_iter
fbdev/sisfb: Constify mode string
fbdev/sisfb: Parse option string with struct option_iter
fbdev/skeletonfb: Parse option string with struct option_iter
fbdev/sm712fb: Duplicate video-mode option string
fbdev/sstfb: Duplicate video-mode option string
fbdev/sstfb: Parse option string with struct option_iter
fbdev/stifb: Remove trailing whitespaces
fbdev/stifb: Constify option string
fbdev/tdfxfb: Duplicate video-mode option string
fbdev/tdfxfb: Parse option string with struct option_iter
fbdev/tgafb: Duplicate video-mode option string
fbdev/tgafb: Parse option string with struct option_iter
fbdev/tmiofb: Remove unused option string
fbdev/tridentfb: Duplicate video-mode option string
fbdev/tridentfb: Parse option string with struct option_iter
fbdev/uvesafb: Duplicate video-mode option string
fbdev/uvesafb: Parse option string with struct option_iter
fbdev/valkyriefb: Remove trailing whitespaces
fbdev/valkyriefb: Parse option string with struct option_iter
fbdev/vermilion: Remove unused option string
fbdev/vesafb: Parse option string with struct option_iter
fbdev/vfb: Remove trailing whitespaces
fbdev/vfb: Duplicate video-mode option string
fbdev/vfb: Parse option string with struct option_iter
fbdev/viafb: Parse option string with struct option_iter
fbdev/vt8623fb: Duplicate video-mode option string
staging/sm750fb: Release g_settings in module-exit function
staging/sm750fb: Duplicate video-mode option string
staging/sm750fb: Parse option string with struct option_iter
fbdev: Constify option strings
Documentation/core-api/kernel-api.rst | 9 ++
drivers/staging/sm750fb/sm750.c | 63 ++++----
drivers/video/fbdev/68328fb.c | 24 +--
drivers/video/fbdev/acornfb.c | 23 ++-
drivers/video/fbdev/amifb.c | 23 +--
drivers/video/fbdev/arkfb.c | 10 +-
drivers/video/fbdev/atafb.c | 21 +--
drivers/video/fbdev/aty/aty128fb.c | 22 ++-
drivers/video/fbdev/aty/atyfb_base.c | 23 ++-
drivers/video/fbdev/aty/radeon_base.c | 26 +--
drivers/video/fbdev/au1100fb.c | 13 +-
drivers/video/fbdev/au1200fb.c | 15 +-
drivers/video/fbdev/cirrusfb.c | 30 ++--
drivers/video/fbdev/controlfb.c | 47 +++---
drivers/video/fbdev/core/fb_cmdline.c | 13 +-
drivers/video/fbdev/core/modedb.c | 8 +-
drivers/video/fbdev/cyber2000fb.c | 17 +-
drivers/video/fbdev/efifb.c | 44 ++---
drivers/video/fbdev/ep93xx-fb.c | 2 +-
drivers/video/fbdev/fm2fb.c | 14 +-
drivers/video/fbdev/fsl-diu-fb.c | 24 +--
drivers/video/fbdev/gbefb.c | 23 +--
drivers/video/fbdev/geode/gx1fb_core.c | 16 +-
drivers/video/fbdev/geode/gxfb_core.c | 23 +--
drivers/video/fbdev/geode/lxfb_core.c | 25 +--
drivers/video/fbdev/grvga.c | 18 ++-
drivers/video/fbdev/gxt4500.c | 13 +-
drivers/video/fbdev/hyperv_fb.c | 18 ++-
drivers/video/fbdev/i740fb.c | 26 +--
drivers/video/fbdev/i810/i810_main.c | 26 ++-
drivers/video/fbdev/imsttfb.c | 16 +-
drivers/video/fbdev/imxfb.c | 21 +--
drivers/video/fbdev/intelfb/intelfbdrv.c | 23 ++-
drivers/video/fbdev/kyro/fbdev.c | 21 ++-
drivers/video/fbdev/macfb.c | 26 +--
drivers/video/fbdev/matrox/matroxfb_base.c | 19 +--
drivers/video/fbdev/mx3fb.c | 23 ++-
drivers/video/fbdev/neofb.c | 26 +--
drivers/video/fbdev/nvidia/nvidia.c | 26 ++-
drivers/video/fbdev/ocfb.c | 21 ++-
drivers/video/fbdev/omap/omapfb_main.c | 15 +-
drivers/video/fbdev/platinumfb.c | 44 ++---
drivers/video/fbdev/pm2fb.c | 25 +--
drivers/video/fbdev/pm3fb.c | 27 ++--
drivers/video/fbdev/ps3fb.c | 28 ++--
drivers/video/fbdev/pvr2fb.c | 32 ++--
drivers/video/fbdev/pxafb.c | 18 ++-
drivers/video/fbdev/riva/fbdev.c | 26 ++-
drivers/video/fbdev/s3fb.c | 27 ++--
drivers/video/fbdev/savage/savagefb_driver.c | 20 ++-
drivers/video/fbdev/sis/sis_main.c | 24 +--
drivers/video/fbdev/skeletonfb.c | 17 +-
drivers/video/fbdev/sm712fb.c | 12 +-
drivers/video/fbdev/sstfb.c | 25 +--
drivers/video/fbdev/stifb.c | 162 +++++++++----------
drivers/video/fbdev/tdfxfb.c | 21 ++-
drivers/video/fbdev/tgafb.c | 30 ++--
drivers/video/fbdev/tmiofb.c | 24 +--
drivers/video/fbdev/tridentfb.c | 27 ++--
drivers/video/fbdev/uvesafb.c | 21 ++-
drivers/video/fbdev/valkyriefb.c | 30 ++--
drivers/video/fbdev/vermilion/vermilion.c | 7 +-
drivers/video/fbdev/vesafb.c | 16 +-
drivers/video/fbdev/vfb.c | 35 ++--
drivers/video/fbdev/via/viafbdev.c | 15 +-
drivers/video/fbdev/vt8623fb.c | 11 +-
include/linux/cmdline.h | 36 +++++
include/linux/fb.h | 2 +-
lib/Makefile | 2 +-
lib/cmdline_iter.c | 109 +++++++++++++
70 files changed, 1087 insertions(+), 682 deletions(-)
create mode 100644 include/linux/cmdline.h
create mode 100644 lib/cmdline_iter.c