{"id":"DEBIAN-CVE-2025-39723","details":"In the Linux kernel, the following vulnerability has been resolved:  netfs: Fix unbuffered write error handling  If all the subrequests in an unbuffered write stream fail, the subrequest collector doesn't update the stream-\u003etransferred value and it retains its initial LONG_MAX value.  Unfortunately, if all active streams fail, then we take the smallest value of { LONG_MAX, LONG_MAX, ... } as the value to set in wreq-\u003etransferred - which is then returned from -\u003ewrite_iter().  LONG_MAX was chosen as the initial value so that all the streams can be quickly assessed by taking the smallest value of all stream-\u003etransferred - but this only works if we've set any of them.  Fix this by adding a flag to indicate whether the value in stream-\u003etransferred is valid and checking that when we integrate the values.  stream-\u003etransferred can then be initialised to zero.  This was found by running the generic/750 xfstest against cifs with cache=none.  It splices data to the target file.  Once (if) it has used up all the available scratch space, the writes start failing with ENOSPC. This causes -\u003ewrite_iter() to fail.  However, it was returning wreq-\u003etransferred, i.e. LONG_MAX, rather than an error (because it thought the amount transferred was non-zero) and iter_file_splice_write() would then try to clean up that amount of pipe bufferage - leading to an oops when it overran.  The kernel log showed:      CIFS: VFS: Send error in write = -28  followed by:      BUG: kernel NULL pointer dereference, address: 0000000000000008  with:      RIP: 0010:iter_file_splice_write+0x3a4/0x520     do_splice+0x197/0x4e0  or:      RIP: 0010:pipe_buf_release (include/linux/pipe_fs_i.h:282)     iter_file_splice_write (fs/splice.c:755)  Also put a warning check into splice to announce if -\u003ewrite_iter() returned that it had written more than it was asked to.","modified":"2026-08-27T23:05:31.580481284Z","published":"2025-09-05T18:15:50.043Z","upstream":["CVE-2025-39723"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2025-39723"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.12.48-1"}]}],"versions":["6.12.38-1","6.12.41-1","6.12.43-1","6.12.43-1~bpo12+1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2025-39723.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.16.5-1"}]}],"versions":["6.12.100-1","6.12.101-1","6.12.105-1","6.12.38-1","6.12.41-1","6.12.43-1","6.12.43-1~bpo12+1","6.12.48-1","6.12.57-1","6.12.57-1~bpo12+1","6.12.63-1","6.12.63-1~bpo12+1","6.12.69-1","6.12.69-1~bpo12+1","6.12.73-1","6.12.73-1~bpo12+1","6.12.74-1","6.12.74-2","6.12.74-2~bpo12+1","6.12.85-1","6.12.85-1~bpo12+1","6.12.86-1","6.12.86-1~bpo12+1","6.12.88-1","6.12.88-1~bpo12+1","6.12.90-1","6.12.90-1~bpo12+1","6.12.90-2","6.12.90-2~bpo12+1","6.12.94-1","6.12.94-1~bpo12+1","6.12.95-1","6.12.95-1~bpo12+1","6.12.96-1","6.13.10-1~exp1","6.13.11-1~exp1","6.13.2-1~exp1","6.13.3-1~exp1","6.13.4-1~exp1","6.13.5-1~exp1","6.13.6-1~exp1","6.13.7-1~exp1","6.13.8-1~exp1","6.13.9-1~exp1","6.13~rc6-1~exp1","6.13~rc7-1~exp1","6.14.3-1~exp1","6.14.5-1~exp1","6.14.6-1~exp1","6.15-1~exp1","6.15.1-1~exp1","6.15.2-1~exp1","6.15.3-1~exp1","6.15.4-1~exp1","6.15.5-1~exp1","6.15.6-1~exp1","6.15~rc7-1~exp1","6.16-1~exp1","6.16.1-1~exp1","6.16.3-1","6.16.3-1~bpo13+1","6.16~rc7-1~exp1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2025-39723.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}