Description
In the Linux kernel, the following vulnerability has been resolved: binfmt_misc: reject a flag character as the field delimiter The registration string starts with a user chosen delimiter that separates the individual fields. So that the field parsers terminate even on a truncated string create_entry() pads the buffer with that same delimiter: memset(buf + count, del, 8); Most fields are scanned for the delimiter with strchr()/scanarg() and happily stop on the padding. The flags field is different: instead of scanning for the delimiter check_special_flags() consumes the flag characters 'P', 'O', 'C' and 'F' and stops at the first byte that is none of them, relying on the trailing delimiter to end the scan. If the delimiter is itself a flag character the padding no longer acts as a terminator. The scan swallows all eight padding bytes and keeps reading past the end of the allocation until it hits a byte that is not a flag character. For example registering PaPEPPxPPiP with 'P' as the delimiter (name "a", type extension, magic "x", interpreter "i", empty flags) leaves the flag scan running off the end of the buffer. The registration is rejected in the end because the parser does not stop exactly at buf + count, but only after the out of bounds read has already happened. With an unlucky allocation layout the scan can walk into an unmapped page; under KASAN it is reported as a slab out of bounds read. binfmt_misc mounts are available to unprivileged users in a user namespace so the read is reachable without privileges. Reject a delimiter that is one of the flag characters up front. Such a registration was always rejected anyway, only after the out of bounds read, so no valid registration string changes meaning.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 96bd5d4fea2970b9b08265293ca7a10b9b27c0fdaffected1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 9970e094e5d60f0d66914bf9a97d1ef19107ebf5affected1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < b29e3c1f375c1296362d219ff38bceddf2d2a88aaffected1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 1819f82dee766c58295ecaacdac02cdf6837d7a4affected1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 1853e95c9bfe69ef1dd862b3f551e68f4a1b76ccaffected1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 840bb9c49c3e75fb32b593d67ab32f6b77122262affected1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 9a2d87db3898b5993b64fd258d0334e0eba9ee0daffected1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 to < 8e85d50ba1117fd446bf9a250bd8a97d48384bdcaffected
Linux Linux
Default version status: affected
2.6.12affected0 to < 2.6.12unaffected5.10.265 to ≤ 5.10.*unaffected5.15.216 to ≤ 5.15.*unaffected6.1.183 to ≤ 6.1.*unaffected6.6.151 to ≤ 6.6.*unaffected6.12.103 to ≤ 6.12.*unaffected6.18.44 to ≤ 6.18.*unaffected7.1.8 to ≤ 7.1.*unaffected7.2 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/96bd5d4fea2970b9b08265293ca7a10b9b27c0fd ↗
- https://git.kernel.org/stable/c/9970e094e5d60f0d66914bf9a97d1ef19107ebf5 ↗
- https://git.kernel.org/stable/c/b29e3c1f375c1296362d219ff38bceddf2d2a88a ↗
- https://git.kernel.org/stable/c/1819f82dee766c58295ecaacdac02cdf6837d7a4 ↗
- https://git.kernel.org/stable/c/1853e95c9bfe69ef1dd862b3f551e68f4a1b76cc ↗
- https://git.kernel.org/stable/c/840bb9c49c3e75fb32b593d67ab32f6b77122262 ↗
- https://git.kernel.org/stable/c/9a2d87db3898b5993b64fd258d0334e0eba9ee0d ↗
- https://git.kernel.org/stable/c/8e85d50ba1117fd446bf9a250bd8a97d48384bdc ↗