While working on extended rand for last_error/first_error timestamps, I noticed that the endianess is wrong, we access the little-endian fields in struct ext4_super_block as native-endian when we print them.
This adds a special case in ext4_attr_show() and ext4_attr_store() to byteswap the superblock fields if needed.
In older kernels, this code was part of super.c, it got moved to sysfs.c in linux-4.4.
Cc: stable@vger.kernel.org Fixes: 52c198c6820f ("ext4: add sysfs entry showing whether the fs contains errors") Signed-off-by: Arnd Bergmann arnd@arndb.de --- fs/ext4/sysfs.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c index f34da0bb8f17..b970a200f20c 100644 --- a/fs/ext4/sysfs.c +++ b/fs/ext4/sysfs.c @@ -274,8 +274,12 @@ static ssize_t ext4_attr_show(struct kobject *kobj, case attr_pointer_ui: if (!ptr) return 0; - return snprintf(buf, PAGE_SIZE, "%u\n", - *((unsigned int *) ptr)); + if (a->attr_ptr == ptr_ext4_super_block_offset) + return snprintf(buf, PAGE_SIZE, "%u\n", + le32_to_cpup(ptr)); + else + return snprintf(buf, PAGE_SIZE, "%u\n", + *((unsigned int *) ptr)); case attr_pointer_atomic: if (!ptr) return 0; @@ -308,7 +312,10 @@ static ssize_t ext4_attr_store(struct kobject *kobj, ret = kstrtoul(skip_spaces(buf), 0, &t); if (ret) return ret; - *((unsigned int *) ptr) = t; + if (a->attr_ptr == ptr_ext4_super_block_offset) + *((__le32 *) ptr) = cpu_to_le32(t); + else + *((unsigned int *) ptr) = t; return len; case attr_inode_readahead: return inode_readahead_blks_store(sbi, buf, len);
On Jun 20, 2018, at 9:32 AM, Arnd Bergmann arnd@arndb.de wrote:
While working on extended rand for last_error/first_error timestamps, I noticed that the endianess is wrong, we access the little-endian fields in struct ext4_super_block as native-endian when we print them.
This adds a special case in ext4_attr_show() and ext4_attr_store() to byteswap the superblock fields if needed.
In older kernels, this code was part of super.c, it got moved to sysfs.c in linux-4.4.
Cc: stable@vger.kernel.org Fixes: 52c198c6820f ("ext4: add sysfs entry showing whether the fs contains errors") Signed-off-by: Arnd Bergmann arnd@arndb.de
I was wondering why this didn't just use le32_to_cpu() all the time, but I see that these functions are being used for both ext4_super_block (on-disk) fields, as well as ext4_sb_info (in-memory) fields. A bit ugly, but I don't think there is a better solution.
Reviewed-by: Andreas Dilger adilger@dilger.ca
fs/ext4/sysfs.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c index f34da0bb8f17..b970a200f20c 100644 --- a/fs/ext4/sysfs.c +++ b/fs/ext4/sysfs.c @@ -274,8 +274,12 @@ static ssize_t ext4_attr_show(struct kobject *kobj, case attr_pointer_ui: if (!ptr) return 0;
return snprintf(buf, PAGE_SIZE, "%u\n",*((unsigned int *) ptr));
if (a->attr_ptr == ptr_ext4_super_block_offset)return snprintf(buf, PAGE_SIZE, "%u\n",le32_to_cpup(ptr));elsereturn snprintf(buf, PAGE_SIZE, "%u\n",*((unsigned int *) ptr));@@ -308,7 +312,10 @@ static ssize_t ext4_attr_store(struct kobject *kobj, ret = kstrtoul(skip_spaces(buf), 0, &t); if (ret) return ret;
*((unsigned int *) ptr) = t;
if (a->attr_ptr == ptr_ext4_super_block_offset)*((__le32 *) ptr) = cpu_to_le32(t);else*((unsigned int *) ptr) = t;-- 2.9.0
Cheers, Andreas
On Thu, Jun 21, 2018 at 7:49 PM, Andreas Dilger adilger@dilger.ca wrote:
On Jun 20, 2018, at 9:32 AM, Arnd Bergmann arnd@arndb.de wrote:
While working on extended rand for last_error/first_error timestamps, I noticed that the endianess is wrong, we access the little-endian fields in struct ext4_super_block as native-endian when we print them.
This adds a special case in ext4_attr_show() and ext4_attr_store() to byteswap the superblock fields if needed.
In older kernels, this code was part of super.c, it got moved to sysfs.c in linux-4.4.
Cc: stable@vger.kernel.org Fixes: 52c198c6820f ("ext4: add sysfs entry showing whether the fs contains errors") Signed-off-by: Arnd Bergmann arnd@arndb.de
I was wondering why this didn't just use le32_to_cpu() all the time, but I see that these functions are being used for both ext4_super_block (on-disk) fields, as well as ext4_sb_info (in-memory) fields. A bit ugly, but I don't think there is a better solution.
Reviewed-by: Andreas Dilger adilger@dilger.ca
One alternative that I considered was to just do away with helpers for the ext4_super_block structure and only use them for ext4_sb_info, especially after the last patch that changes this again. However, as a bugfix for stable backports it seemed best to keep the change as simple as possible.
Thanks for the review,
Arnd
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