kernel/linux.git/lib/mpi/mpicoder.c, branch v5.15.210

lib/crypto: mpi: Fix integer underflow in mpi_read_raw_from_sgl()

2026-06-19T11:33:39+00:00

commit 8c2f1288250a90a4b5cabed5d888d7e3aeed4035 upstream. 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 2d4d1eea540b ("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 63ba4d67594a ("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 # off-list Fixes: 2d4d1eea540b ("lib/mpi: Add mpi sgl helpers") Signed-off-by: Lukas Wunner Cc: stable@vger.kernel.org # v4.4+ Reviewed-by: Ignat Korchagin Reviewed-by: Jarkko Sakkinen Link: https://lore.kernel.org/r/59eca92ff4f87e2081777f1423a0efaaadcfdb39.1776003111.git.lukas@wunner.de Signed-off-by: Eric Biggers Signed-off-by: Greg Kroah-Hartman

lib/mpi: Fix buffer overrun when SG is too long

2023-03-10T08:39:09+00:00

[ Upstream commit 7361d1bc307b926cbca214ab67b641123c2d6357 ] The helper mpi_read_raw_from_sgl sets the number of entries in the SG list according to nbytes. However, if the last entry in the SG list contains more data than nbytes, then it may overrun the buffer because it only allocates enough memory for nbytes. Fixes: 2d4d1eea540b ("lib/mpi: Add mpi sgl helpers") Reported-by: Roberto Sassu Signed-off-by: Herbert Xu Reviewed-by: Eric Biggers Signed-off-by: Herbert Xu Signed-off-by: Sasha Levin

lib/mpi: fix spelling mistakes

2021-07-01T18:06:05+00:00

Fix some spelling mistakes in comments: flaged ==> flagged bufer ==> buffer multipler ==> multiplier MULTIPLER ==> MULTIPLIER leaset ==> least chnage ==> change Link: https://lkml.kernel.org/r/20210604074401.12198-1-thunder.leizhen@huawei.com Signed-off-by: Zhen Lei Cc: Herbert Xu Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

lib/mpi: Extend the MPI library

2020-09-25T07:48:53+00:00

Expand the mpi library based on libgcrypt, and the ECC algorithm of mpi based on libgcrypt requires these functions. Some other algorithms will be developed based on mpi ecc, such as SM2. Signed-off-by: Tianjia Zhang Tested-by: Xufeng Zhang Signed-off-by: Herbert Xu

lib/mpi: kunmap after finishing accessing buffer

2017-08-22T06:45:01+00:00

Using sg_miter_start and sg_miter_next, the buffer of an SG is kmap'ed to *buff. The current code calls sg_miter_stop (and thus kunmap) on the SG entry before the last access of *buff. The patch moves the sg_miter_stop call after the last access to *buff to ensure that the memory pointed to by *buff is still mapped. Fixes: 4816c9406430 ("lib/mpi: Fix SG miter leak") Cc: Signed-off-by: Stephan Mueller Signed-off-by: Herbert Xu

lib/mpi: Fix SG miter leak

2016-07-29T10:30:16+00:00

In mpi_read_raw_from_sgl we may leak the SG miter resouces after reading the leading zeroes. This patch fixes this by stopping the iteration once the leading zeroes have been read. Fixes: 127827b9c295 ("lib/mpi: Do not do sg_virt") Reported-by: Nicolai Stange Tested-by: Nicolai Stange Signed-off-by: Herbert Xu

lib/mpi: Do not do sg_virt

2016-07-01T15:45:18+00:00

Currently the mpi SG helpers use sg_virt which is completely broken. It happens to work with normal kernel memory but will fail with anything that is not linearly mapped. This patch fixes this by using the SG iterator helpers. Signed-off-by: Herbert Xu

crypto: rsa - Generate fixed-length output

2016-07-01T15:45:18+00:00

Every implementation of RSA that we have naturally generates output with leading zeroes. The one and only user of RSA, pkcs1pad wants to have those leading zeroes in place, in fact because they are currently absent it has to write those zeroes itself. So we shouldn't be stripping leading zeroes in the first place. In fact this patch makes rsa-generic produce output with fixed length so that pkcs1pad does not need to do any extra work. This patch also changes DH to use the new interface. Signed-off-by: Herbert Xu

lib/mpi: refactor mpi_read_from_buffer() in terms of mpi_read_raw_data()

2016-05-31T08:42:01+00:00

mpi_read_from_buffer() and mpi_read_raw_data() do basically the same thing except that the former extracts the number of payload bits from the first two bytes of the input buffer. Besides that, the data copying logic is exactly the same. Replace the open coded buffer to MPI instance conversion by a call to mpi_read_raw_data(). Signed-off-by: Nicolai Stange Signed-off-by: Herbert Xu

lib/mpi: mpi_read_from_buffer(): sanitize short buffer printk

2016-05-31T08:42:00+00:00

The first two bytes of the input buffer encode its expected length and mpi_read_from_buffer() prints a console message if the given buffer is too short. However, there are some oddities with how this message is printed: - It is printed at the default loglevel. This is different from the one used in the case that the first two bytes' value is unsupportedly large, i.e. KERN_INFO. - The format specifier '%d' is used for unsigned ints. - It prints the values of nread and *ret_nread. This is redundant since the former is always the latter + 1. Clean this up as follows: - Use pr_info() rather than printk() with no loglevel. - Use the format specifiers '%u' in place if '%d'. - Do not print the redundant 'nread' but the more helpful 'nbytes' value. Signed-off-by: Nicolai Stange Signed-off-by: Herbert Xu