Description (CNA)
In the Linux kernel, the following vulnerability has been resolved: dm-verity-fec: fix reading parity bytes split across blocks (take 3) fec_decode_bufs() assumes that the parity bytes of the first RS codeword it decodes are never split across parity blocks. This assumption is false. Consider v->fec->block_size == 4096 && v->fec->roots == 17 && fio->nbufs == 1, for example. In that case, each call to fec_decode_bufs() consumes v->fec->roots * (fio->nbufs << DM_VERITY_FEC_BUF_RS_BITS) = 272 parity bytes. Considering that the parity data for each message block starts on a block boundary, the byte alignment in the parity data will iterate through 272*i mod 4096 until the 3 parity blocks have been consumed. On the 16th call (i=15), the alignment will be 4080 bytes into the first block. Only 16 bytes remain in that block, but 17 parity bytes will be needed. The code reads out-of-bounds from the parity block buffer. Fortunately this doesn't normally happen, since it can occur only for certain non-default values of fec_roots *and* when the maximum number of buffers couldn't be allocated due to low memory. For example with block_size=4096 only the following cases are affected: fec_roots=17: nbufs in [1, 3, 5, 15] fec_roots=19: nbufs in [1, 229] fec_roots=21: nbufs in [1, 3, 5, 13, 15, 39, 65, 195] fec_roots=23: nbufs in [1, 89] Regardless, fix it by refactoring how the parity blocks are read.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 12caa73a28f0ae147ec0356b45091edf2462462b before 03348b440f69417dc3a3c71d8271cff6b05f67fb; affected fc8943886629e26de34867db302c74d465510826 before dac69d1b76049d7e5f565089a6a7f4502a85b9de; affected 6df90c02bae468a3a6110bafbc659884d0c4966c before d47281b9a4472cfd73122393e79fbe76b651e46a; affected 6df90c02bae468a3a6110bafbc659884d0c4966c before 3d1b4e2d8ac0a1a1390a117f61ce0ca1c47e3bcb; affected 6df90c02bae468a3a6110bafbc659884d0c4966c before 430a05cb926f6bdf53e81460a2c3a553257f3f61; affected 6bc6ee31113b05db605694491bdeb2b1730142f1; affected 6.6.72 before 6.6.160; affected 6.12.10 before 6.12.114; affected 6.1.125 before 6.2 |
| Linux / Linux | affected 6.13; unaffected 0 before 6.13; unaffected 6.6.160 through 6.6.*; unaffected 6.12.114 through 6.12.*; unaffected 6.18.42 through 6.18.*; unaffected 7.0.7 through 7.0.*; unaffected 7.1 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/03348b440f69417dc3a3c71d8271cff6b05f67fb
- https://git.kernel.org/stable/c/dac69d1b76049d7e5f565089a6a7f4502a85b9de
- https://git.kernel.org/stable/c/d47281b9a4472cfd73122393e79fbe76b651e46a
- https://git.kernel.org/stable/c/3d1b4e2d8ac0a1a1390a117f61ce0ca1c47e3bcb
- https://git.kernel.org/stable/c/430a05cb926f6bdf53e81460a2c3a553257f3f61