Re: fsck segfaults on rpi3 running 13-stable (and on 14-CURRENT analyzing the same file system that resulted from the 13-STABLE crash)
Date: Tue, 14 Feb 2023 19:29:28 UTC
John-Mark Gurney wrote this message on Mon, Feb 13, 2023 at 15:25 -0800: After analyzing the remaining crashes that were detected, the following was found.. This was done w/ a minimal FS, It is possible that it'll find more crashes w/ a slightly more complex FS, e.g. one w/ indirect blocks, and other file types. Note that FS's that exhibit these are available at: https://www.funkthat.com/~jmg/FreeBSD/ffs.afl/ ---- FIRST ---- std_checkblkavail doesn't check that blkno is within valid range, e.g. if blkno is negative, it'll segfault: 0x0000000000121d6c in std_checkblkavail (blkno=blkno@entry=-288230376151711688, frags=frags@entry=1) at /usr/src/sbin/fsck_ffs/fsutil.c:1149 1149 if (testbmap(blkno + j)) ---- SECOND ---- pass5 doesn't check that cg_nextfreeoff is sane/within range, this causes a large value to be passed to memset, in this case: #1 0x000000000012fee4 in pass5 () at /usr/src/sbin/fsck_ffs/pass5.c:241 241 memset(cg_inosused(newcg), 0, (size_t)(mapsize)); (gdb) print *newcg $7 = {cg_firstfield = 0, cg_magic = 590421, cg_old_time = 0, cg_cgx = 0, cg_old_ncyl = 0, cg_old_niblk = 0, cg_ndblk = 256, cg_cs = {cs_ndir = 0, cs_nbfree = 0, cs_nifree = 128, cs_nffree = 0}, cg_rotor = 0, cg_frotor = 0, cg_irotor = 0, cg_frsum = {0, 0, 0, 0, 0, 0, 0, 0}, cg_old_btotoff = 0, cg_old_boff = 0, cg_iusedoff = 168, cg_freeoff = 184, cg_nextfreeoff = 61341980, cg_clustersumoff = 54526164, cg_clusteroff = 54526232, cg_nclusterblks = 32, cg_niblk = 128, cg_initediblk = 128, cg_unrefs = 0, cg_sparecon32 = {0}, cg_ckhash = 3548071837, cg_time = 1676327229, cg_sparecon64 = {0, 0, 0}, cg_space = ""} and mapsize is: (gdb) print newcg->cg_nextfreeoff - newcg->cg_iusedoff $6 = 61341812 which overflows buf, which is MAXBSIZE, or 8k. ---- THIRD ---- allocino doesn't make sure that cg_iusedoff is sane. In this case, cg_iusedoff is 4294965672, which means that in allocino, the setbit function call will access invalid memory. 0x0000000000127168 in allocino (request=2, type=16877) at /usr/src/sbin/fsck_ffs/inode.c:1379 1379 setbit(cg_inosused(cgp), ino % sblock.fs_ipg); (gdb) print *cgp $14 = {cg_firstfield = 0, cg_magic = 590421, cg_old_time = 0, cg_cgx = 0, cg_old_ncyl = 0, cg_old_niblk = 0, cg_ndblk = 256, cg_cs = {cs_ndir = 2, cs_nbfree = 23, cs_nifree = 124, cs_nffree = 21}, cg_rotor = 0, cg_frotor = 0, cg_irotor = 0, cg_frsum = {0, 0, 0, 0, 0, 0, 0, 3}, cg_old_btotoff = 0, cg_old_boff = 0, cg_iusedoff = 4294965672, cg_freeoff = 183, cg_nextfreeoff = 284, cg_clustersumoff = 212, cg_clusteroff = 280, cg_nclusterblks = 32, cg_niblk = 128, cg_initediblk = 128, cg_unrefs = 0, cg_sparecon32 = {0}, cg_ckhash = 3548071837, cg_time = 1676327229, cg_sparecon64 = {0, 0, 0}, cg_space = "\017"} -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."