| Message ID | cover.1703324146.git.wqu@suse.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | kstrtox: introduce memparse_safe() | expand |
On Sat, Dec 23, 2023 at 08:28:04PM +1030, Qu Wenruo wrote: > Function memparse() lacks error handling: > > - If no valid number string at all > In that case @retptr would just be updated and return value would be > zero. > > - No overflown detection > This applies to both the number string part, and the suffixes part. > And since we have no way to indicate errors, we can get weird results > like: > > "25E" -> 10376293541461622784 (9E) > > This is due to the fact that for "E" suffix, there is only 4 bits > left, and 25 with 60 bits left shift would lead to overflow. > (And decision to support for that "E" suffix is already cursed) > > So here we introduce a safer version of it: memparse_safe(), and mark > the original one deprecated. > Unfortunately I didn't find a good way to mark it deprecated, as with > recent -Werror changes, '__deprecated' marco does not seem to warn > anymore. > > The new helper has the following advantages: > > - Better overflow and invalid string detection > The overflow detection is for both the numberic part, and with the > suffix. Thus above "25E" would be rejected correctly. > The invalid string part means if there is no valid number starts at > the buffer, we return -EINVAL. > > - Allow caller to select the suffixes, and saner default ones > The new default one would be "KMGTP", without the cursed and overflow > prone "E". > Some older code like setup_elfcorehdr() would benefit from it, if the > code really wants to only allow "KMG" suffixes. > > - Keep the old @retptr behavior > So the existing callers can easily migrate to the new one, without the > need to do extra strsep() work. > > - Finally test cases > The test case would cover more things other than the existing kstrtox > tests: > * The @retptr behavior > Either for bad cases, which @retptr should not be touched, > or for good cases, the @retptr is properly advanced, > > * Return value verification > Make sure we distinguish -EINVAL and -ERANGE correctly. > > With the new helper, migrate btrfs to the interface, and since the > @retptr behavior is the same, we won't cause any behavior change. Thank you for the prompt update, I will be off till end of January, and in any case this is material for v6.9+, so I will look at this afterwards.
Function memparse() lacks error handling: - If no valid number string at all In that case @retptr would just be updated and return value would be zero. - No overflown detection This applies to both the number string part, and the suffixes part. And since we have no way to indicate errors, we can get weird results like: "25E" -> 10376293541461622784 (9E) This is due to the fact that for "E" suffix, there is only 4 bits left, and 25 with 60 bits left shift would lead to overflow. (And decision to support for that "E" suffix is already cursed) So here we introduce a safer version of it: memparse_safe(), and mark the original one deprecated. Unfortunately I didn't find a good way to mark it deprecated, as with recent -Werror changes, '__deprecated' marco does not seem to warn anymore. The new helper has the following advantages: - Better overflow and invalid string detection The overflow detection is for both the numberic part, and with the suffix. Thus above "25E" would be rejected correctly. The invalid string part means if there is no valid number starts at the buffer, we return -EINVAL. - Allow caller to select the suffixes, and saner default ones The new default one would be "KMGTP", without the cursed and overflow prone "E". Some older code like setup_elfcorehdr() would benefit from it, if the code really wants to only allow "KMG" suffixes. - Keep the old @retptr behavior So the existing callers can easily migrate to the new one, without the need to do extra strsep() work. - Finally test cases The test case would cover more things other than the existing kstrtox tests: * The @retptr behavior Either for bad cases, which @retptr should not be touched, or for good cases, the @retptr is properly advanced, * Return value verification Make sure we distinguish -EINVAL and -ERANGE correctly. With the new helper, migrate btrfs to the interface, and since the @retptr behavior is the same, we won't cause any behavior change. Qu Wenruo (3): kstrtox: introduce a safer version of memparse() kstrtox: add unit tests for memparse_safe() btrfs: migrate to the newer memparse_safe() helper fs/btrfs/ioctl.c | 8 +- fs/btrfs/super.c | 8 ++ fs/btrfs/sysfs.c | 14 ++- include/linux/kernel.h | 8 +- include/linux/kstrtox.h | 15 +++ lib/cmdline.c | 5 +- lib/kstrtox.c | 96 ++++++++++++++++++ lib/test-kstrtox.c | 217 ++++++++++++++++++++++++++++++++++++++++ 8 files changed, 364 insertions(+), 7 deletions(-)