Vasily Averin 4acbbe98e0 pstore: pstore_ftrace_seq_next should increase position index ... commit 6c871b7314dde9ab64f20de8f5aa3d01be4518e8 upstream. In Aug 2018 NeilBrown noticed commit 1f4aace60b ("fs/seq_file.c: simplify seq_file iteration code and interface") "Some ->next functions do not increment *pos when they return NULL... Note that such ->next functions are buggy and should be fixed. A simple demonstration is dd if=/proc/swaps bs=1000 skip=1 Choose any block size larger than the size of /proc/swaps. This will always show the whole last line of /proc/swaps" /proc/swaps output was fixed recently, however there are lot of other affected files, and one of them is related to pstore subsystem. If .next function does not change position index, following .show function will repeat output related to current position index. There are at least 2 related problems: - read after lseek beyond end of file, described above by NeilBrown "dd if=<AFFECTED_FILE> bs=1000 skip=1" will generate whole last list - read after lseek on in middle of last line will output expected rest of last line but then repeat whole last line once again. If .show() function generates multy-line output (like pstore_ftrace_seq_show() does ?) following bash script cycles endlessly $ q=;while read -r r;do echo "$((++q)) $r";done < AFFECTED_FILE Unfortunately I'm not familiar enough to pstore subsystem and was unable to find affected pstore-related file on my test node. If .next function does not change position index, following .show function will repeat output related to current position index. Cc: stable@vger.kernel.org Fixes: 1f4aace60b ("fs/seq_file.c: simplify seq_file iteration code ...") Link: https://bugzilla.kernel.org/show_bug.cgi?id=206283 Signed-off-by: Vasily Averin <vvs@virtuozzo.com> Link: https://lore.kernel.org/r/4e49830d-4c88-0171-ee24-1ee540028dad@virtuozzo.com [kees: with robustness tweak from Joel Fernandes <joelaf@google.com>] Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2020-04-17 10:50:12 +02:00
..
Kconfig	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00
Makefile	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
ftrace.c	pstore: no need to check return value of debugfs_create functions	2019-07-08 21:04:42 -07:00
inode.c	pstore: pstore_ftrace_seq_next should increase position index	2020-04-17 10:50:12 +02:00
internal.h	pstore: Centralize init/exit routines	2018-10-22 07:11:58 -07:00
platform.c	pstore/platform: fix potential mem leak if pstore_init_fs failed	2020-04-17 10:50:03 +02:00
pmsg.c	treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 282	2019-06-05 17:36:37 +02:00
ram.c	pstore/ram: Regularize prz label allocation lifetime	2020-01-14 20:08:28 +01:00
ram_core.c	pstore/ram: Regularize prz label allocation lifetime	2020-01-14 20:08:28 +01:00