Описание
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: require minimum ACE size in smb_check_perm_dacl()
Both ACE-walk loops in smb_check_perm_dacl() only guard against an
under-sized remaining buffer, not against an ACE whose declared
ace->size is smaller than the struct it claims to describe:
if (offsetof(struct smb_ace, access_req) > aces_size)
break;
ace_size = le16_to_cpu(ace->size);
if (ace_size > aces_size)
break;
The first check only requires the 4-byte ACE header to be in bounds;
it does not require access_req (4 bytes at offset 4) to be readable.
An attacker who has set a crafted DACL on a file they own can declare
ace->size == 4 with aces_size == 4, pass both checks, and then
granted |= le32_to_cpu(ace->access_req); /* upper loop /
compare_sids(&sid, &ace->sid); / lower loop */
reads access_req at offset 4 (OOB by up to 4 bytes) and ace->sid at
offset 8 (OOB by up to CIFS_SID_BASE_SIZE + SID_MAX_SUB_AUTHORITIES
- 4 bytes).
Tighten both loops to require
ace_size >= offsetof(struct smb_ace, sid) + CIFS_SID_BASE_SIZE
which is the smallest valid on-wire ACE layout (4-byte header +
4-byte access_req + 8-byte sid base with zero sub-auths). Also
reject ACEs whose sid.num_subauth exceeds SID_MAX_SUB_AUTHORITIES
before letting compare_sids() dereference sub_auth[] entries.
parse_sec_desc() already enforces an equivalent check (lines 441-448);
smb_check_perm_dacl() simply grew weaker validation over time.
Reachability: authenticated SMB client with permission to set an ACL
on a file. On a subsequent CREATE against that file, the kernel
walks the stored DACL via smb_check_perm_dacl() and triggers the
OOB read. Not pre-auth, and the OOB read is not reflected to the
attacker, but KASAN reports and kernel state corruption are
possible.
A flaw was found in the ksmbd component of the Linux kernel. An authenticated Server Message Block (SMB) client with permissions to set an Access Control List (ACL) on a file can craft a malicious Discretionary Access Control List (DACL). This crafted DACL, containing an undersized Access Control Entry (ACE), can lead to an out-of-bounds read when the kernel processes it during a subsequent file creation operation. This vulnerability could result in kernel state corruption.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Not affected | ||
| Red Hat Enterprise Linux 6 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Not affected |
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Дополнительная информация
EPSS
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: ksmbd: require minimum ACE size in smb_check_perm_dacl() Both ACE-walk loops in smb_check_perm_dacl() only guard against an under-sized remaining buffer, not against an ACE whose declared `ace->size` is smaller than the struct it claims to describe: if (offsetof(struct smb_ace, access_req) > aces_size) break; ace_size = le16_to_cpu(ace->size); if (ace_size > aces_size) break; The first check only requires the 4-byte ACE header to be in bounds; it does not require access_req (4 bytes at offset 4) to be readable. An attacker who has set a crafted DACL on a file they own can declare ace->size == 4 with aces_size == 4, pass both checks, and then granted |= le32_to_cpu(ace->access_req); /* upper loop */ compare_sids(&sid, &ace->sid); /* lower loop */ reads access_req at offset 4 (OOB by up to 4 bytes) and ace->sid at offset 8 (OOB by up to CIFS_SID_BASE_SIZE + SID_MAX_SUB_AUTHORITIES...
In the Linux kernel, the following vulnerability has been resolved: ksmbd: require minimum ACE size in smb_check_perm_dacl() Both ACE-walk loops in smb_check_perm_dacl() only guard against an under-sized remaining buffer, not against an ACE whose declared `ace->size` is smaller than the struct it claims to describe: if (offsetof(struct smb_ace, access_req) > aces_size) break; ace_size = le16_to_cpu(ace->size); if (ace_size > aces_size) break; The first check only requires the 4-byte ACE header to be in bounds; it does not require access_req (4 bytes at offset 4) to be readable. An attacker who has set a crafted DACL on a file they own can declare ace->size == 4 with aces_size == 4, pass both checks, and then granted |= le32_to_cpu(ace->access_req); /* upper loop */ compare_sids(&sid, &ace->sid); /* lower loop */ reads access_req at offset 4 (OOB by up to 4 bytes) and ace->sid at offset 8 (OOB by up to CIFS_SID_BASE_SIZE
In the Linux kernel, the following vulnerability has been resolved: k ...
In the Linux kernel, the following vulnerability has been resolved: ksmbd: require minimum ACE size in smb_check_perm_dacl() Both ACE-walk loops in smb_check_perm_dacl() only guard against an under-sized remaining buffer, not against an ACE whose declared `ace->size` is smaller than the struct it claims to describe: if (offsetof(struct smb_ace, access_req) > aces_size) break; ace_size = le16_to_cpu(ace->size); if (ace_size > aces_size) break; The first check only requires the 4-byte ACE header to be in bounds; it does not require access_req (4 bytes at offset 4) to be readable. An attacker who has set a crafted DACL on a file they own can declare ace->size == 4 with aces_size == 4, pass both checks, and then granted |= le32_to_cpu(ace->access_req); /* upper loop */ compare_sids(&sid, &ace->sid); /* lower loop */ reads access_req at offset 4 (OOB by up to 4 bytes) and ace->sid at offset 8 (OOB by up to CIFS_SID_BASE_SI...
EPSS