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sysctl: handle error writing UINT_MAX to u32 fields

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We have scripts which write to certain fields on 3.18 kernels but this
seems to be failing on 4.4 kernels.  An entry which we write to here is
xfrm_aevent_rseqth which is u32.

  echo 4294967295  > /proc/sys/net/core/xfrm_aevent_rseqth

Commit 230633d109 ("kernel/sysctl.c: detect overflows when converting
to int") prevented writing to sysctl entries when integer overflow
occurs.  However, this does not apply to unsigned integers.

Heinrich suggested that we introduce a new option to handle 64 bit
limits and set min as 0 and max as UINT_MAX.  This might not work as it
leads to issues similar to __do_proc_doulongvec_minmax.  Alternatively,
we would need to change the datatype of the entry to 64 bit.

  static int __do_proc_doulongvec_minmax(void *data, struct ctl_table
  {
      i = (unsigned long *) data;   //This cast is causing to read beyond the size of data (u32)
      vleft = table->maxlen / sizeof(unsigned long); //vleft is 0 because maxlen is sizeof(u32) which is lesser than sizeof(unsigned long) on x86_64.

Introduce a new proc handler proc_douintvec.  Individual proc entries
will need to be updated to use the new handler.

[akpm@linux-foundation.org: coding-style fixes]
Fixes: 230633d109 ("kernel/sysctl.c:detect overflows when converting to int")
Link: http://lkml.kernel.org/r/1471479806-5252-1-git-send-email-subashab@codeaurora.org
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Subash Abhinov Kasiviswanathan 2016-08-25 15:16:51 -07:00 committed by Linus Torvalds
parent 8582fb59f7
commit e7d316a02f
2 changed files with 45 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/sysctl.h
View File

@ -42,6 +42,8 @@ extern int proc_dostring(struct ctl_table *, int,
void __user *, size_t *, loff_t *);
extern int proc_dointvec(struct ctl_table *, int,
void __user *, size_t *, loff_t *);
extern int proc_douintvec(struct ctl_table *, int,
void __user *, size_t *, loff_t *);
extern int proc_dointvec_minmax(struct ctl_table *, int,
void __user *, size_t *, loff_t *);
extern int proc_dointvec_jiffies(struct ctl_table *, int,

45
kernel/sysctl.c
View File

@ -2140,6 +2140,21 @@ static int do_proc_dointvec_conv(bool *negp, unsigned long *lvalp,
return 0;
}
static int do_proc_douintvec_conv(bool *negp, unsigned long *lvalp,
int *valp,
int write, void *data)
{
if (write) {
if (*negp)
return -EINVAL;
*valp = *lvalp;
} else {
unsigned int val = *valp;
*lvalp = (unsigned long)val;
}
return 0;
}
static const char proc_wspace_sep[] = { ' ', '\t', '\n' };
static int __do_proc_dointvec(void *tbl_data, struct ctl_table *table,
@ -2259,8 +2274,27 @@ static int do_proc_dointvec(struct ctl_table *table, int write,
int proc_dointvec(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
return do_proc_dointvec(table,write,buffer,lenp,ppos,
NULL,NULL);
return do_proc_dointvec(table, write, buffer, lenp, ppos, NULL, NULL);
}
/**
* proc_douintvec - read a vector of unsigned integers
* @table: the sysctl table
* @write: %TRUE if this is a write to the sysctl file
* @buffer: the user buffer
* @lenp: the size of the user buffer
* @ppos: file position
*
* Reads/writes up to table->maxlen/sizeof(unsigned int) unsigned integer
* values from/to the user buffer, treated as an ASCII string.
*
* Returns 0 on success.
*/
int proc_douintvec(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
return do_proc_dointvec(table, write, buffer, lenp, ppos,
do_proc_douintvec_conv, NULL);
}
/*
@ -2858,6 +2892,12 @@ int proc_dointvec(struct ctl_table *table, int write,
return -ENOSYS;
}
int proc_douintvec(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
return -ENOSYS;
}
int proc_dointvec_minmax(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
@ -2903,6 +2943,7 @@ int proc_doulongvec_ms_jiffies_minmax(struct ctl_table *table, int write,
* exception granted :-)
*/
EXPORT_SYMBOL(proc_dointvec);
EXPORT_SYMBOL(proc_douintvec);
EXPORT_SYMBOL(proc_dointvec_jiffies);
EXPORT_SYMBOL(proc_dointvec_minmax);
EXPORT_SYMBOL(proc_dointvec_userhz_jiffies);