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sched/debug: Fix memory corruption caused by multiple small reads of flags

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Reading /proc/sys/kernel/sched_domain/cpu*/domain0/flags mutliple times
with small reads causes oopses with slub corruption issues because the kfree is
free'ing an offset from a previous allocation. Fix this by adding in a new
pointer 'buf' for the allocation and kfree and use the temporary pointer tmp
to handle memory copies of the buf offsets.

Fixes: 5b9f8ff7b3 ("sched/debug: Output SD flag names rather than their values")
Reported-by: Jeff Bastian <jbastian@redhat.com>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20201029151103.373410-1-colin.king@canonical.com
This commit is contained in:
Colin Ian King 2020-10-29 15:11:03 +00:00 committed by Peter Zijlstra
parent b4c9c9f156
commit 8d4d9c7b43
1 changed files with 6 additions and 6 deletions
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12
kernel/sched/debug.c
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@ -251,7 +251,7 @@ static int sd_ctl_doflags(struct ctl_table *table, int write,
unsigned long flags = *(unsigned long *)table->data;
size_t data_size = 0;
size_t len = 0;
char *tmp;
char *tmp, *buf;
int idx;
if (write)
@ -269,17 +269,17 @@ static int sd_ctl_doflags(struct ctl_table *table, int write,
return 0;
}
tmp = kcalloc(data_size + 1, sizeof(*tmp), GFP_KERNEL);
if (!tmp)
buf = kcalloc(data_size + 1, sizeof(*buf), GFP_KERNEL);
if (!buf)
return -ENOMEM;
for_each_set_bit(idx, &flags, __SD_FLAG_CNT) {
char *name = sd_flag_debug[idx].name;
len += snprintf(tmp + len, strlen(name) + 2, "%s ", name);
len += snprintf(buf + len, strlen(name) + 2, "%s ", name);
}
tmp += *ppos;
tmp = buf + *ppos;
len -= *ppos;
if (len > *lenp)
@ -294,7 +294,7 @@ static int sd_ctl_doflags(struct ctl_table *table, int write,
*lenp = len;
*ppos += len;
kfree(tmp);
kfree(buf);
return 0;
}