Yiming reports an integer underflow in mpi_read_raw_from_sgl() when
subtracting "lzeros" from the unsigned "nbytes".
For this to happen, the scatterlist "sgl" needs to occupy more bytes
than the "nbytes" parameter and the first "nbytes + 1" bytes of the
scatterlist must be zero. Under these conditions, the while loop
iterating over the scatterlist will count more zeroes than "nbytes",
subtract the number of zeroes from "nbytes" and cause the underflow.
When commit 2d4d1eea54 ("lib/mpi: Add mpi sgl helpers") originally
introduced the bug, it couldn't be triggered because all callers of
mpi_read_raw_from_sgl() passed a scatterlist whose length was equal to
"nbytes".
However since commit 63ba4d6759 ("KEYS: asymmetric: Use new crypto
interface without scatterlists"), the underflow can now actually be
triggered. When invoking a KEYCTL_PKEY_ENCRYPT system call with a
larger "out_len" than "in_len" and filling the "in" buffer with zeroes,
crypto_akcipher_sync_prep() will create an all-zero scatterlist used for
both the "src" and "dst" member of struct akcipher_request and thereby
fulfil the conditions to trigger the bug:
sys_keyctl()
keyctl_pkey_e_d_s()
asymmetric_key_eds_op()
software_key_eds_op()
crypto_akcipher_sync_encrypt()
crypto_akcipher_sync_prep()
crypto_akcipher_encrypt()
rsa_enc()
mpi_read_raw_from_sgl()
To the user this will be visible as a DoS as the kernel spins forever,
causing soft lockup splats as a side effect.
Fix it.
Reported-by: Yiming Qian <yimingqian591@gmail.com> # off-list
Fixes: 2d4d1eea54 ("lib/mpi: Add mpi sgl helpers")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: stable@vger.kernel.org # v4.4+
Reviewed-by: Ignat Korchagin <ignat@linux.win>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Link: https://lore.kernel.org/r/59eca92ff4f87e2081777f1423a0efaaadcfdb39.1776003111.git.lukas@wunner.de
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
min_t(unsigned int, a, b) casts an 'unsigned long' to 'unsigned int'.
Use min(a, b) instead as it promotes any 'unsigned int' to 'unsigned long'
and so cannot discard significant bits.
In this case the 'unsigned long' value is small enough that the result
is ok.
Detected by an extra check added to min_t().
Signed-off-by: David Laight <david.laight.linux@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Fix build warnings with W=1 that started appearing after
commit a934a57a42 ("scripts/misc-check: check missing #include
<linux/export.h> when W=1").
While at it, also sort the include lists alphabetically. (Keep
asm/irqflags.h last, as otherwise it doesn't build on alpha.)
This handles all of lib/crypto/, but not arch/*/lib/crypto/. The
exports in arch/*/lib/crypto/ will go away when the code is properly
integrated into lib/crypto/ as planned.
Link: https://lore.kernel.org/r/20250613184814.50173-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
This partially reverts commit a8ea8bdd9d.
Most of it is no longer needed since sm2 has been removed. However,
the following functions have been kept as they have developed other
uses:
mpi_copy
mpi_mod
mpi_test_bit
mpi_set_bit
mpi_rshift
mpi_add
mpi_sub
mpi_addm
mpi_subm
mpi_mul
mpi_mulm
mpi_tdiv_r
mpi_fdiv_r
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
As lib/mpi is mostly used by crypto code, move it under lib/crypto
so that patches touching it get directed to the right mailing list.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
