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sysctl: check for UINT_MAX before unsigned int min/max 

Mikulas noticed in the existing do_proc_douintvec_minmax_conv() and
do_proc_dopipe_max_size_conv() introduced in this patchset, that they
inconsistently handle overflow and min/max range inputs:

For example:

  0 ... param->min - 1 ---> ERANGE
  param->min ... param->max ---> the value is accepted
  param->max + 1 ... 0x100000000L + param->min - 1 ---> ERANGE
  0x100000000L + param->min ... 0x100000000L + param->max ---> EINVAL
  0x100000000L + param->max + 1, 0x200000000L + param->min - 1 ---> ERANGE
  0x200000000L + param->min ... 0x200000000L + param->max ---> EINVAL
  0x200000000L + param->max + 1, 0x300000000L + param->min - 1 ---> ERANGE

In do_proc_do*() routines which store values into unsigned int variables
(4 bytes wide for 64-bit builds), first validate that the input unsigned
long value (8 bytes wide for 64-bit builds) will fit inside the smaller
unsigned int variable.  Then check that the unsigned int value falls
inside the specified parameter min, max range.  Otherwise the unsigned
long -> unsigned int conversion drops leading bits from the input value,
leading to the inconsistent pattern Mikulas documented above.

Link: http://lkml.kernel.org/r/1507658689-11669-5-git-send-email-joe.lawrence@redhat.com
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@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:
Joe Lawrence 2017-11-17 15:29:28 -08:00 committed by Linus Torvalds
parent 7a8d181949
commit fb910c42cc
1 changed files with 8 additions and 6 deletions
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14
kernel/sysctl.c
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@ -2576,12 +2576,13 @@ static int do_proc_douintvec_minmax_conv(unsigned long *lvalp,
if (write) {
unsigned int val = *lvalp;
if (*lvalp > UINT_MAX)
return -EINVAL;
if ((param->min && *param->min > val) ||
(param->max && *param->max < val))
return -ERANGE;
if (*lvalp > UINT_MAX)
return -EINVAL;
*valp = val;
} else {
unsigned int val = *valp;
@ -2632,17 +2633,18 @@ static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
struct do_proc_dopipe_max_size_conv_param *param = data;
if (write) {
unsigned int val = round_pipe_size(*lvalp);
unsigned int val;
if (*lvalp > UINT_MAX)
return -EINVAL;
val = round_pipe_size(*lvalp);
if (val == 0)
return -EINVAL;
if (param->min && *param->min > val)
return -ERANGE;
if (*lvalp > UINT_MAX)
return -EINVAL;
*valp = val;
} else {
unsigned int val = *valp;