CVE-2025-38415

In the Linux kernel, the following vulnerability has been resolved: Squashfs: check return result of sb_min_blocksize Syzkaller reports an "UBSAN: shift-out-of-bounds in squashfs_bio_read" bug. Syzkaller forks multiple processes which after mounting the Squashfs filesystem, issues an ioctl("/dev/loop0", LOOP_SET_BLOCK_SIZE, 0x8000). Now if this ioctl occurs at the same time another process is in the process of mounting a Squashfs filesystem on /dev/loop0, the failure occurs. When this happens the following code in squashfs_fill_super() fails. ---- msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE); msblk->devblksize_log2 = ffz(~msblk->devblksize); ---- sb_min_blocksize() returns 0, which means msblk->devblksize is set to 0. As a result, ffz(~msblk->devblksize) returns 64, and msblk->devblksize_log2 is set to 64. This subsequently causes the UBSAN: shift-out-of-bounds in fs/squashfs/block.c:195:36 shift exponent 64 is too large for 64-bit type 'u64' (aka 'unsigned long long') This commit adds a check for a 0 return by sb_min_blocksize().

In the Linux kernel, the following vulnerability has been resolved: Squashfs: check return result of sb_min_blocksize Syzkaller reports an "UBSAN: shift-out-of-bounds in squashfs_bio_read" bug. Syzkaller forks multiple processes which after mounting the Squashfs filesystem, issues an ioctl("/dev/loop0", LOOP_SET_BLOCK_SIZE, 0x8000). Now if this ioctl occurs at the same time another process is in the process of mounting a Squashfs filesystem on /dev/loop0, the failure occurs. When this happens the following code in squashfs_fill_super() fails. ---- msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE); msblk->devblksize_log2 = ffz(~msblk->devblksize); ---- sb_min_blocksize() returns 0, which means msblk->devblksize is set to 0. As a result, ffz(~msblk->devblksize) returns 64, and msblk->devblksize_log2 is set to 64. This subsequently causes the UBSAN: shift-out-of-bounds in fs/squashfs/block.c:195:36 shift exponent 64 is too large for 64-bit type 'u64' (aka 'unsigned long long') This commit adds a check for a 0 return by sb_min_blocksize().

En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: Squashfs: comprobar el resultado devuelto de sb_min_blocksize. Syzkaller informa del error "UBSAN: desplazamiento fuera de los límites en squashfs_bio_read". Syzkaller bifurca varios procesos que, tras montar el sistema de archivos Squashfs, emiten una instrucción ioctl("/dev/loop0", LOOP_SET_BLOCK_SIZE, 0x8000). Si esta instrucción ioctl se produce al mismo tiempo que otro proceso está montando un sistema de archivos Squashfs en /dev/loop0, se produce el fallo. En este caso, el siguiente código en squashfs_fill_super() falla: ---- msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE); msblk->devblksize_log2 = ffz(~msblk->devblksize); ---- sb_min_blocksize() devuelve 0, lo que significa que msblk->devblksize está establecido en 0. Como resultado, ffz(~msblk->devblksize) devuelve 64 y msblk->devblksize_log2 está establecido en 64. Esto posteriormente provoca el UBSAN: shift-out-of-bounds en fs/squashfs/block.c:195:36 el exponente de desplazamiento 64 es demasiado grande para el tipo de 64 bits 'u64' (también conocido como 'unsigned long long') Esta confirmación agrega una comprobación para un retorno de 0 por sb_min_blocksize().