Messages in this thread | | | From | Vasily Averin <> | Subject | [PATCH 0/7] seq_file .next functions should increase position index | Date | Fri, 24 Jan 2020 10:02:36 +0300 |
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In Aug 2018 NeilBrown noticed commit 1f4aace60b0e ("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"
Described problem is still actual. If you make lseek into middle of last output line following read will output end of last line and whole last line once again.
$ dd if=/proc/swaps bs=1 # usual output Filename Type Size Used Priority /dev/dm-0 partition 4194812 97536 -2 104+0 records in 104+0 records out 104 bytes copied
$ dd if=/proc/swaps bs=40 skip=1 # last line was generated twice dd: /proc/swaps: cannot skip to specified offset v/dm-0 partition 4194812 97536 -2 /dev/dm-0 partition 4194812 97536 -2 3+1 records in 3+1 records out 131 bytes copied
There are lot of other affected files, I've found 30+ including /proc/net/ip_tables_matches and /proc/sysvipc/*
I've sent patches into maillists of affected subsystems already, this patch-set fixes the problem in files related to pstore, tracing, gcov, sysvipc and other subsystems processed via linux-kernel@ mailing list directly
https://bugzilla.kernel.org/show_bug.cgi?id=206283
Vasily Averin (7): pstore_ftrace_seq_next should increase position index gcov_seq_next should increase position index t_next should increase position index fpid_next should increase position index eval_map_next should increase position index trigger_next should increase position index sysvipc_find_ipc should increase position index
fs/pstore/inode.c | 2 +- ipc/util.c | 2 +- kernel/gcov/fs.c | 2 +- kernel/trace/ftrace.c | 9 ++++++--- kernel/trace/trace.c | 4 +--- kernel/trace/trace_events_trigger.c | 5 +++-- 6 files changed, 13 insertions(+), 11 deletions(-)
-- 1.8.3.1
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