https://github.com/torvalds/linux
Revision 86d32f9a7c54ad74f4514d7fef7c847883207291 authored by Vasily Averin on 14 April 2020, 20:33:16 UTC, committed by Linus Torvalds on 16 April 2020, 17:10:50 UTC
If seq_file .next function does not change position index, read after some lseek can generate unexpected output: $ dd if=/proc/keys bs=1 # full usual output 0f6bfdf5 I--Q--- 2 perm 3f010000 1000 1000 user 4af2f79ab8848d0a: 740 1fb91b32 I--Q--- 3 perm 1f3f0000 1000 65534 keyring _uid.1000: 2 27589480 I--Q--- 1 perm 0b0b0000 0 0 user invocation_id: 16 2f33ab67 I--Q--- 152 perm 3f030000 0 0 keyring _ses: 2 33f1d8fa I--Q--- 4 perm 3f030000 1000 1000 keyring _ses: 1 3d427fda I--Q--- 2 perm 3f010000 1000 1000 user 69ec44aec7678e5a: 740 3ead4096 I--Q--- 1 perm 1f3f0000 1000 65534 keyring _uid_ses.1000: 1 521+0 records in 521+0 records out 521 bytes copied, 0,00123769 s, 421 kB/s But a read after lseek in middle of last line results in the partial last line and then a repeat of the final line: $ dd if=/proc/keys bs=500 skip=1 dd: /proc/keys: cannot skip to specified offset g _uid_ses.1000: 1 3ead4096 I--Q--- 1 perm 1f3f0000 1000 65534 keyring _uid_ses.1000: 1 0+1 records in 0+1 records out 97 bytes copied, 0,000135035 s, 718 kB/s and a read after lseek beyond end of file results in the last line being shown: $ dd if=/proc/keys bs=1000 skip=1 # read after lseek beyond end of file dd: /proc/keys: cannot skip to specified offset 3ead4096 I--Q--- 1 perm 1f3f0000 1000 65534 keyring _uid_ses.1000: 1 0+1 records in 0+1 records out 76 bytes copied, 0,000119981 s, 633 kB/s See https://bugzilla.kernel.org/show_bug.cgi?id=206283 Fixes: 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code ...") Signed-off-by: Vasily Averin <vvs@virtuozzo.com> Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 0008633
Tip revision: 86d32f9a7c54ad74f4514d7fef7c847883207291 authored by Vasily Averin on 14 April 2020, 20:33:16 UTC
keys: Fix proc_keys_next to increase position index
keys: Fix proc_keys_next to increase position index
Tip revision: 86d32f9
bsearch.c
// SPDX-License-Identifier: GPL-2.0-only
/*
* A generic implementation of binary search for the Linux kernel
*
* Copyright (C) 2008-2009 Ksplice, Inc.
* Author: Tim Abbott <tabbott@ksplice.com>
*/
#include <linux/export.h>
#include <linux/bsearch.h>
#include <linux/kprobes.h>
/*
* bsearch - binary search an array of elements
* @key: pointer to item being searched for
* @base: pointer to first element to search
* @num: number of elements
* @size: size of each element
* @cmp: pointer to comparison function
*
* This function does a binary search on the given array. The
* contents of the array should already be in ascending sorted order
* under the provided comparison function.
*
* Note that the key need not have the same type as the elements in
* the array, e.g. key could be a string and the comparison function
* could compare the string with the struct's name field. However, if
* the key and elements in the array are of the same type, you can use
* the same comparison function for both sort() and bsearch().
*/
void *bsearch(const void *key, const void *base, size_t num, size_t size,
cmp_func_t cmp)
{
const char *pivot;
int result;
while (num > 0) {
pivot = base + (num >> 1) * size;
result = cmp(key, pivot);
if (result == 0)
return (void *)pivot;
if (result > 0) {
base = pivot + size;
num--;
}
num >>= 1;
}
return NULL;
}
EXPORT_SYMBOL(bsearch);
NOKPROBE_SYMBOL(bsearch);
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