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Neither checks the returned length before using it. If mtd_read() ever returns success with retlen 0 for a nonzero request, romfs_mtd_strnlen() makes no progress on maxlen/pos/n and loops forever. romfs_mtd_strcmp() decrements the size_t length by one to drop the padding byte it asked for; with retlen 0 that underflows to SIZE_MAX, and the following memcmp()/buf[len] run far outside the 16/17-byte stack buffers. romfs_mtd_read() already treats "rlen != buflen" as -EIO for plain reads; apply the same requirement here so a short read is rejected instead of silently mishandled. Fixes: da4458bda237 ("NOMMU: Make it possible for RomFS to use MTD devices directly") Signed-off-by: Muhammad Bilal --- fs/romfs/storage.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/romfs/storage.c b/fs/romfs/storage.c index b57b3ffcbc32..6313e218b8da 100644 --- a/fs/romfs/storage.c +++ b/fs/romfs/storage.c @@ -48,6 +48,8 @@ static ssize_t romfs_mtd_strnlen(struct super_block *sb, ret = ROMFS_MTD_READ(sb, pos, segment, &len, buf); if (ret < 0) return ret; + if (len != segment) + return -EIO; p = memchr(buf, 0, len); if (p) return n + (p - buf); @@ -79,6 +81,8 @@ static int romfs_mtd_strcmp(struct super_block *sb, unsigned long pos, ret = ROMFS_MTD_READ(sb, pos, segment, &len, buf); if (ret < 0) return ret; + if (len != segment) + return -EIO; len--; if (memcmp(buf, str, len) != 0) return 0; -- 2.55.0