Nicolai Stange 0bb5c9ead6 lib/mpi: mpi_read_raw_from_sgl(): fix out-of-bounds buffer access ... Within the copying loop in mpi_read_raw_from_sgl(), the last input SGE's byte count gets artificially extended as follows: if (sg_is_last(sg) && (len % BYTES_PER_MPI_LIMB)) len += BYTES_PER_MPI_LIMB - (len % BYTES_PER_MPI_LIMB); Within the following byte copying loop, this causes reads beyond that SGE's allocated buffer: BUG: KASAN: slab-out-of-bounds in mpi_read_raw_from_sgl+0x331/0x650 at addr ffff8801e168d4d8 Read of size 1 by task systemd-udevd/721 [...] Call Trace: [<ffffffff818c4d35>] dump_stack+0xbc/0x117 [<ffffffff818c4c79>] ? _atomic_dec_and_lock+0x169/0x169 [<ffffffff814af5d1>] ? print_section+0x61/0xb0 [<ffffffff814b1109>] print_trailer+0x179/0x2c0 [<ffffffff814bc524>] object_err+0x34/0x40 [<ffffffff814bfdc7>] kasan_report_error+0x307/0x8c0 [<ffffffff814bf315>] ? kasan_unpoison_shadow+0x35/0x50 [<ffffffff814bf38e>] ? kasan_kmalloc+0x5e/0x70 [<ffffffff814c0ad1>] kasan_report+0x71/0xa0 [<ffffffff81938171>] ? mpi_read_raw_from_sgl+0x331/0x650 [<ffffffff814bf1a6>] __asan_load1+0x46/0x50 [<ffffffff81938171>] mpi_read_raw_from_sgl+0x331/0x650 [<ffffffff817f41b6>] rsa_verify+0x106/0x260 [<ffffffff817f40b0>] ? rsa_set_pub_key+0xf0/0xf0 [<ffffffff818edc79>] ? sg_init_table+0x29/0x50 [<ffffffff817f4d22>] ? pkcs1pad_sg_set_buf+0xb2/0x2e0 [<ffffffff817f5b74>] pkcs1pad_verify+0x1f4/0x2b0 [<ffffffff81831057>] public_key_verify_signature+0x3a7/0x5e0 [<ffffffff81830cb0>] ? public_key_describe+0x80/0x80 [<ffffffff817830f0>] ? keyring_search_aux+0x150/0x150 [<ffffffff818334a4>] ? x509_request_asymmetric_key+0x114/0x370 [<ffffffff814b83f0>] ? kfree+0x220/0x370 [<ffffffff818312c2>] public_key_verify_signature_2+0x32/0x50 [<ffffffff81830b5c>] verify_signature+0x7c/0xb0 [<ffffffff81835d0c>] pkcs7_validate_trust+0x42c/0x5f0 [<ffffffff813c391a>] system_verify_data+0xca/0x170 [<ffffffff813c3850>] ? top_trace_array+0x9b/0x9b [<ffffffff81510b29>] ? __vfs_read+0x279/0x3d0 [<ffffffff8129372f>] mod_verify_sig+0x1ff/0x290 [...] The exact purpose of the len extension isn't clear to me, but due to its form, I suspect that it's a leftover somehow accounting for leading zero bytes within the most significant output limb. Note however that without that len adjustement, the total number of bytes ever processed by the inner loop equals nbytes and thus, the last output limb gets written at this point. Thus the net effect of the len adjustement cited above is just to keep the inner loop running for some more iterations, namely < BYTES_PER_MPI_LIMB ones, reading some extra bytes from beyond the last SGE's buffer and discarding them afterwards. Fix this issue by purging the extension of len beyond the last input SGE's buffer length. Fixes: 2d4d1eea54 ("lib/mpi: Add mpi sgl helpers") Signed-off-by: Nicolai Stange <nicstange@gmail.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>		2016-04-05 20:35:51 +08:00
..
generic_mpih-add1.c
generic_mpih-lshift.c
generic_mpih-mul1.c
generic_mpih-mul2.c
generic_mpih-mul3.c
generic_mpih-rshift.c
generic_mpih-sub1.c
longlong.h	lib/mpi: avoid assembler warning	2016-02-28 03:26:34 +08:00
Makefile	MPILIB: Reinstate mpi_cmp[_ui]() and export for RSA signature verification	2012-10-08 13:50:15 +10:30
mpi-bit.c	MPILIB: Provide count_leading/trailing_zeros() based on arch functions	2012-10-08 13:50:11 +10:30
mpi-cmp.c	MPILIB: Fix comparison of negative MPIs	2015-01-14 16:10:12 +00:00
mpi-inline.h	lib/mpi: use "static inline" instead of "extern inline"	2016-02-28 03:26:34 +08:00
mpi-internal.h	lib/mpi: use "static inline" instead of "extern inline"	2016-02-28 03:26:34 +08:00
mpi-pow.c	MPILIB: Provide count_leading/trailing_zeros() based on arch functions	2012-10-08 13:50:11 +10:30
mpicoder.c	lib/mpi: mpi_read_raw_from_sgl(): fix out-of-bounds buffer access	2016-04-05 20:35:51 +08:00
mpih-cmp.c
mpih-div.c	Remove unused code from MPI library	2012-05-26 11:51:03 +10:00
mpih-mul.c	Remove unused code from MPI library	2012-05-26 11:51:03 +10:00
mpiutil.c	MPILIB: add mpi_read_buf() and mpi_get_size() helpers	2015-06-16 14:35:06 +08:00