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f2fs: protect extension_list reading with sb_lock in f2fs_sbi_show()

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In f2fs_sbi_show(), the extension_list, extension_count and
hot_ext_count are read without holding sbi->sb_lock. If a concurrent
sysfs store modifies the extension list via f2fs_update_extension_list(),
the show path may read inconsistent count and array contents, potentially
leading to out-of-bounds access or displaying stale data.

Fix this by holding sb_lock around the entire extension list read
and format operation.

Fixes: b6a06cbbb5 ("f2fs: support hot file extension")
Signed-off-by: Yongpeng Yang <yangyongpeng@xiaomi.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This commit is contained in:
Yongpeng Yang
2026-04-10 23:05:39 +08:00
committed by Jaegeuk Kim
parent b8b902fd57
commit 5909bedbed
1 changed files with 5 additions and 2 deletions
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7
fs/f2fs/sysfs.c
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@@ -387,10 +387,12 @@ static ssize_t f2fs_sbi_show(struct f2fs_attr *a,
if (!strcmp(a->attr.name, "extension_list")) {
__u8 (*extlist)[F2FS_EXTENSION_LEN] =
sbi->raw_super->extension_list;
int cold_count = le32_to_cpu(sbi->raw_super->extension_count);
int hot_count = sbi->raw_super->hot_ext_count;
int cold_count, hot_count;
int len = 0, i;
f2fs_down_read(&sbi->sb_lock);
cold_count = le32_to_cpu(sbi->raw_super->extension_count);
hot_count = sbi->raw_super->hot_ext_count;
len += sysfs_emit_at(buf, len, "cold file extension:\n");
for (i = 0; i < cold_count; i++)
len += sysfs_emit_at(buf, len, "%s\n", extlist[i]);
@@ -398,6 +400,7 @@ static ssize_t f2fs_sbi_show(struct f2fs_attr *a,
len += sysfs_emit_at(buf, len, "hot file extension:\n");
for (i = cold_count; i < cold_count + hot_count; i++)
len += sysfs_emit_at(buf, len, "%s\n", extlist[i]);
f2fs_up_read(&sbi->sb_lock);
return len;
}