CVE-2024-26688

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> fs,hugetlb: fix NULL pointer dereference in hugetlbs_fill_super<br /> <br /> When configuring a hugetlb filesystem via the fsconfig() syscall, there is<br /> a possible NULL dereference in hugetlbfs_fill_super() caused by assigning<br /> NULL to ctx-&gt;hstate in hugetlbfs_parse_param() when the requested pagesize<br /> is non valid.<br /> <br /> E.g: Taking the following steps:<br /> <br /> fd = fsopen("hugetlbfs", FSOPEN_CLOEXEC);<br /> fsconfig(fd, FSCONFIG_SET_STRING, "pagesize", "1024", 0);<br /> fsconfig(fd, FSCONFIG_CMD_CREATE, NULL, NULL, 0);<br /> <br /> Given that the requested "pagesize" is invalid, ctxt-&gt;hstate will be replaced<br /> with NULL, losing its previous value, and we will print an error:<br /> <br /> ...<br /> ...<br /> case Opt_pagesize:<br /> ps = memparse(param-&gt;string, &amp;rest);<br /> ctx-&gt;hstate = h;<br /> if (!ctx-&gt;hstate) {<br /> pr_err("Unsupported page size %lu MB\n", ps / SZ_1M);<br /> return -EINVAL;<br /> }<br /> return 0;<br /> ...<br /> ...<br /> <br /> This is a problem because later on, we will dereference ctxt-&gt;hstate in<br /> hugetlbfs_fill_super()<br /> <br /> ...<br /> ...<br /> sb-&gt;s_blocksize = huge_page_size(ctx-&gt;hstate);<br /> ...<br /> ...<br /> <br /> Causing below Oops.<br /> <br /> Fix this by replacing cxt-&gt;hstate value only when then pagesize is known<br /> to be valid.<br /> <br /> kernel: hugetlbfs: Unsupported page size 0 MB<br /> kernel: BUG: kernel NULL pointer dereference, address: 0000000000000028<br /> kernel: #PF: supervisor read access in kernel mode<br /> kernel: #PF: error_code(0x0000) - not-present page<br /> kernel: PGD 800000010f66c067 P4D 800000010f66c067 PUD 1b22f8067 PMD 0<br /> kernel: Oops: 0000 [#1] PREEMPT SMP PTI<br /> kernel: CPU: 4 PID: 5659 Comm: syscall Tainted: G E 6.8.0-rc2-default+ #22 5a47c3fef76212addcc6eb71344aabc35190ae8f<br /> kernel: Hardware name: Intel Corp. GROVEPORT/GROVEPORT, BIOS GVPRCRB1.86B.0016.D04.1705030402 05/03/2017<br /> kernel: RIP: 0010:hugetlbfs_fill_super+0xb4/0x1a0<br /> kernel: Code: 48 8b 3b e8 3e c6 ed ff 48 85 c0 48 89 45 20 0f 84 d6 00 00 00 48 b8 ff ff ff ff ff ff ff 7f 4c 89 e7 49 89 44 24 20 48 8b 03 48 28 b8 00 10 00 00 48 d3 e0 49 89 44 24 18 48 8b 03 8b 40 28<br /> kernel: RSP: 0018:ffffbe9960fcbd48 EFLAGS: 00010246<br /> kernel: RAX: 0000000000000000 RBX: ffff9af5272ae780 RCX: 0000000000372004<br /> kernel: RDX: ffffffffffffffff RSI: ffffffffffffffff RDI: ffff9af555e9b000<br /> kernel: RBP: ffff9af52ee66b00 R08: 0000000000000040 R09: 0000000000370004<br /> kernel: R10: ffffbe9960fcbd48 R11: 0000000000000040 R12: ffff9af555e9b000<br /> kernel: R13: ffffffffa66b86c0 R14: ffff9af507d2f400 R15: ffff9af507d2f400<br /> kernel: FS: 00007ffbc0ba4740(0000) GS:ffff9b0bd7000000(0000) knlGS:0000000000000000<br /> kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033<br /> kernel: CR2: 0000000000000028 CR3: 00000001b1ee0000 CR4: 00000000001506f0<br /> kernel: Call Trace:<br /> kernel: <br /> kernel: ? __die_body+0x1a/0x60<br /> kernel: ? page_fault_oops+0x16f/0x4a0<br /> kernel: ? search_bpf_extables+0x65/0x70<br /> kernel: ? fixup_exception+0x22/0x310<br /> kernel: ? exc_page_fault+0x69/0x150<br /> kernel: ? asm_exc_page_fault+0x22/0x30<br /> kernel: ? __pfx_hugetlbfs_fill_super+0x10/0x10<br /> kernel: ? hugetlbfs_fill_super+0xb4/0x1a0<br /> kernel: ? hugetlbfs_fill_super+0x28/0x1a0<br /> kernel: ? __pfx_hugetlbfs_fill_super+0x10/0x10<br /> kernel: vfs_get_super+0x40/0xa0<br /> kernel: ? __pfx_bpf_lsm_capable+0x10/0x10<br /> kernel: vfs_get_tree+0x25/0xd0<br /> kernel: vfs_cmd_create+0x64/0xe0<br /> kernel: __x64_sys_fsconfig+0x395/0x410<br /> kernel: do_syscall_64+0x80/0x160<br /> kernel: ? syscall_exit_to_user_mode+0x82/0x240<br /> kernel: ? do_syscall_64+0x8d/0x160<br /> kernel: ? syscall_exit_to_user_mode+0x82/0x240<br /> kernel: ? do_syscall_64+0x8d/0x160<br /> kernel: ? exc_page_fault+0x69/0x150<br /> kernel: entry_SYSCALL_64_after_hwframe+0x6e/0x76<br /> kernel: RIP: 0033:0x7ffbc0cb87c9<br /> kernel: Code: 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 3d 01 f0 ff ff 73 01 c3 48 8b 0d 97 96 0d 00 f7 d8 64 89 01 48<br /> kernel: RSP: 002b:00007ffc29d2f388 EFLAGS: 00000206 ORIG_RAX: 00000000000001af<br /> kernel: RAX: fffffffffff<br /> ---truncated---