From 2ac0baab4aff1a0b45067d0b62f00c15f4e86856 Mon Sep 17 00:00:00 2001 From: Miquel Raynal Date: Thu, 9 Jun 2022 16:02:06 +0200 Subject: [PATCH] fs/squashfs: sqfs_read: Prevent arbitrary code execution Following Jincheng's report, an out-of-band write leading to arbitrary code execution is possible because on one side the squashfs logic accepts directory names up to 65535 bytes (u16), while U-Boot fs logic accepts directory names up to 255 bytes long. Prevent such an exploit from happening by capping directory name sizes to 255. Use a define for this purpose so that developers can link the limitation to its source and eventually kill it some day by dynamically allocating this array (if ever desired). Link: https://lore.kernel.org/all/CALO=DHFB+yBoXxVr5KcsK0iFdg+e7ywko4-e+72kjbcS8JBfPw@mail.gmail.com Reported-by: Jincheng Wang Signed-off-by: Miquel Raynal Tested-by: Jincheng Wang --- fs/squashfs/sqfs.c | 8 +++++--- include/fs.h | 4 +++- 2 files changed, 8 insertions(+), 4 deletions(-) diff --git a/fs/squashfs/sqfs.c b/fs/squashfs/sqfs.c index 547d2fd4b3..b9f05efd9c 100644 --- a/fs/squashfs/sqfs.c +++ b/fs/squashfs/sqfs.c @@ -975,6 +975,7 @@ int sqfs_readdir(struct fs_dir_stream *fs_dirs, struct fs_dirent **dentp) int i_number, offset = 0, ret; struct fs_dirent *dent; unsigned char *ipos; + u16 name_size; dirs = (struct squashfs_dir_stream *)fs_dirs; if (!dirs->size) { @@ -1057,9 +1058,10 @@ int sqfs_readdir(struct fs_dir_stream *fs_dirs, struct fs_dirent **dentp) return -SQFS_STOP_READDIR; } - /* Set entry name */ - strncpy(dent->name, dirs->entry->name, dirs->entry->name_size + 1); - dent->name[dirs->entry->name_size + 1] = '\0'; + /* Set entry name (capped at FS_DIRENT_NAME_LEN which is a U-Boot limitation) */ + name_size = min_t(u16, dirs->entry->name_size + 1, FS_DIRENT_NAME_LEN - 1); + strncpy(dent->name, dirs->entry->name, name_size); + dent->name[name_size] = '\0'; offset = dirs->entry->name_size + 1 + SQFS_ENTRY_BASE_LENGTH; dirs->entry_count--; diff --git a/include/fs.h b/include/fs.h index b43f16a692..2195dc172e 100644 --- a/include/fs.h +++ b/include/fs.h @@ -174,6 +174,8 @@ int fs_write(const char *filename, ulong addr, loff_t offset, loff_t len, #define FS_DT_REG 8 /* regular file */ #define FS_DT_LNK 10 /* symbolic link */ +#define FS_DIRENT_NAME_LEN 256 + /** * struct fs_dirent - directory entry * @@ -194,7 +196,7 @@ struct fs_dirent { /** change_time: time of last modification */ struct rtc_time change_time; /** name: file name */ - char name[256]; + char name[FS_DIRENT_NAME_LEN]; }; /* Note: fs_dir_stream should be treated as opaque to the user of fs layer */ -- 2.39.5