Bug 259112

Summary: A damaged ext3 inode with bad extents can cause a kernel page fault.
Product: Base System Reporter: Robert Morris <rtm>
Component: kernAssignee: Neel Chauhan <nc>
Status: Closed FIXED    
Severity: Affects Only Me CC: emaste, fsu, nc
Priority: ---    
Version: CURRENT   
Hardware: Any   
OS: Any   
URL: https://reviews.freebsd.org/D33030
Attachments:
Description Flags
A damaged ext3 file system that causes a kernel page fault. none

Description Robert Morris 2021-10-12 19:00:59 UTC 
Created attachment 228634 [details]
A damaged ext3 file system that causes a kernel page fault.

If a damaged ext3 inode claims to have extents with
depth greater than 5, ext4_ext_find_extent() &c can run
off the end of the paths array. ext4_ext_check_header()
should probably check eh_depth.

I've attached a demo:

# uname -a
FreeBSD stock14 14.0-CURRENT FreeBSD 14.0-CURRENT #0 main-n248636-d20e9e02db3: Thu Aug 12 05:47:18 UTC 2021     root@releng1.nyi.freebsd.org:/usr/obj/usr/src/amd64.amd64/sys/GENERIC  amd64
# gunzip ext310.img.gz 
# mdconfig -f ext310.img
# mount -t ext2fs -o ro /dev/md0 /mnt
# cp /mnt/a /dev/null
Fatal trap 12: page fault while in kernel mode
cpuid = 0; apic id = 00
fault virtual address   = 0xffff80403fffc000
fault code              = supervisor read data, page not present
instruction pointer     = 0x20:0xffffffff810c2d23
stack pointer           = 0x28:0xfffffe009bba7350
frame pointer           = 0x28:0xfffffe009bba7350
code segment            = base rx0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 871 (cp)
trap number             = 12
panic: page fault
cpuid = 0
time = 1634064958
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe009bba6ff0
vpanic() at vpanic+0x187/frame 0xfffffe009bba7050
panic() at panic+0x43/frame 0xfffffe009bba70b0
trap_fatal() at trap_fatal+0x387/frame 0xfffffe009bba7110
trap_pfault() at trap_pfault+0x99/frame 0xfffffe009bba7170
trap() at trap+0x2a7/frame 0xfffffe009bba7280
calltrap() at calltrap+0x8/frame 0xfffffe009bba7280
--- trap 0xc, rip = 0xffffffff810c2d23, rsp = 0xfffffe009bba7350, rbp = 0xfffffe009bba7350 ---
pmap_kextract() at pmap_kextract+0x1d3/frame 0xfffffe009bba7350
free() at free+0x52/frame 0xfffffe009bba7380
ext4_ext_find_extent() at ext4_ext_find_extent+0x45f/frame 0xfffffe009bba7400
ext4_bmapext() at ext4_bmapext+0x97/frame 0xfffffe009bba7460
ext2_strategy() at ext2_strategy+0x5b/frame 0xfffffe009bba7490
bufstrategy() at bufstrategy+0x3e/frame 0xfffffe009bba74c0
breadn_flags() at breadn_flags+0x1a3/frame 0xfffffe009bba7530
ext2_blkatoff() at ext2_blkatoff+0x56/frame 0xfffffe009bba75b0
ext2_lookup_ino() at ext2_lookup_ino+0x2af/frame 0xfffffe009bba76c0
vfs_cache_lookup() at vfs_cache_lookup+0xa6/frame 0xfffffe009bba7710
lookup() at lookup+0x4a1/frame 0xfffffe009bba77b0
namei() at namei+0x358/frame 0xfffffe009bba7870
kern_statat() at kern_statat+0x12d/frame 0xfffffe009bba79c0
sys_fstatat() at sys_fstatat+0x2f/frame 0xfffffe009bba7ac0
amd64_syscall() at amd64_syscall+0x12e/frame 0xfffffe009bba7bf0
fast_syscall_common() at fast_syscall_common+0xf8/frame 0xfffffe009bba7bf0
Comment 1 commit-hook freebsd_committer freebsd_triage 2021-11-18 17:55:00 UTC 
A commit in branch main references this bug:

URL: https://cgit.FreeBSD.org/src/commit/?id=be60d8f276fa20fc11ad814e54c9c2540f79c7da

commit be60d8f276fa20fc11ad814e54c9c2540f79c7da
Author:     Neel Chauhan <nc@FreeBSD.org>
AuthorDate: 2021-11-17 00:25:04 +0000
Commit:     Neel Chauhan <nc@FreeBSD.org>
CommitDate: 2021-11-18 17:54:42 +0000

    ext2fs: check for eh_depth in ext4_ext_check_header()

    PR:                     259112
    Reported by:            Robert Morris <rtm@lcs.mit.edu>
    Reviewed by:            fsu
    MFC after:              3 days
    Differential Revision:  https://reviews.freebsd.org/D33030

 sys/fs/ext2fs/ext2_extents.c | 4 ++++
 1 file changed, 4 insertions(+)
Comment 2 Neel Chauhan freebsd_committer freebsd_triage 2021-11-18 17:55:27 UTC 
Committed!
Comment 3 commit-hook freebsd_committer freebsd_triage 2021-11-29 17:57:43 UTC 
A commit in branch stable/13 references this bug:

URL: https://cgit.FreeBSD.org/src/commit/?id=5c50e93e6ce43e8558e043de0745bad889c3a77f

commit 5c50e93e6ce43e8558e043de0745bad889c3a77f
Author:     Neel Chauhan <nc@FreeBSD.org>
AuthorDate: 2021-11-17 00:25:04 +0000
Commit:     Neel Chauhan <nc@FreeBSD.org>
CommitDate: 2021-11-29 17:56:42 +0000

    ext2fs: check for eh_depth in ext4_ext_check_header()

    PR:                     259112
    Reported by:            Robert Morris <rtm@lcs.mit.edu>
    Reviewed by:            fsu (src)
    Differential Revision:  https://reviews.freebsd.org/D33030

    (cherry picked from commit be60d8f276fa20fc11ad814e54c9c2540f79c7da)

 sys/fs/ext2fs/ext2_extents.c | 4 ++++
 1 file changed, 4 insertions(+)
Comment 4 commit-hook freebsd_committer freebsd_triage 2021-11-29 17:57:44 UTC 
A commit in branch stable/12 references this bug:

URL: https://cgit.FreeBSD.org/src/commit/?id=8facf7082d4973aedc30cdd8e90fbd33beb17d7f

commit 8facf7082d4973aedc30cdd8e90fbd33beb17d7f
Author:     Neel Chauhan <nc@FreeBSD.org>
AuthorDate: 2021-11-17 00:25:04 +0000
Commit:     Neel Chauhan <nc@FreeBSD.org>
CommitDate: 2021-11-29 17:57:12 +0000

    ext2fs: check for eh_depth in ext4_ext_check_header()

    PR:                     259112
    Reported by:            Robert Morris <rtm@lcs.mit.edu>
    Reviewed by:            fsu (src)
    Differential Revision:  https://reviews.freebsd.org/D33030

    (cherry picked from commit be60d8f276fa20fc11ad814e54c9c2540f79c7da)

 sys/fs/ext2fs/ext2_extents.c | 4 ++++
 1 file changed, 4 insertions(+)
Comment 5 commit-hook freebsd_committer freebsd_triage 2021-12-30 06:16:00 UTC 
A commit in branch main references this bug:

URL: https://cgit.FreeBSD.org/src/commit/?id=f1d5e2c862ef599efd1705b04d505d5415b77f82

commit f1d5e2c862ef599efd1705b04d505d5415b77f82
Author:     Fedor Uporov <fsu@FreeBSD.org>
AuthorDate: 2021-12-24 14:18:15 +0000
Commit:     Fedor Uporov <fsu@FreeBSD.org>
CommitDate: 2021-12-30 06:14:45 +0000

    Improve extents verification logic

    Add functionality for extents validation inside the filesystem
    extents block. The main logic is implemented under
    ext4_validate_extent_entries() function, which verifies extents
    or extents indexes depending of extent depth value.

    PR:                     259112
    Reported by:            Robert Morris
    Reviewed by:            pfg
    MFC after:              2 weeks
    Differential Revision:  https://reviews.freebsd.org/D33375

 sys/fs/ext2fs/ext2_extents.c   | 291 +++++++++++++++++++++++++++++++----------
 sys/fs/ext2fs/ext2_inode_cnv.c |   8 +-
 2 files changed, 224 insertions(+), 75 deletions(-)