sadc crashes on a mtab file with really long lines #162
Comments
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Hi Robert, Thank you for your bug report and your patch. Regards, |
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@sysstat how can I change sysstat.ioconf to avoid the segment fault, not merge the patch version 11.2.0 ubuntu 16.04. Fixed at https://launchpad.net/ubuntu/+source/sysstat/11.2.0-1ubuntu0.2 |
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Fixing the problem requires applying the patch, not changing sysstat.ioconf. |
TL-Yao
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A segmentation fault may happen with "sadc -S DISK..." or "sadc -S XDISK..." when lines longer than 512 bytes are read from /etc/mtab. Such lines are possible for instance when overlay2 filesystem with docker is used. In such a case a single mtab entry can look like this (note that new line characters were added for readability, the original entry contained only one '\n' at the end): overlay /var/lib/docker/overlay2/f23d2377a67b9ab1b49555ecd09b2ccdc03 7e0ee5d9e54f87e59f07f4398e71f/merged overlay rw,relatime,lowerdir=/v ar/lib/docker/overlay2/l/L6VKIYXWBQSJ5R7V35SS43R6Y6:/var/lib/docker/ overlay2/l/UCCHKGXUJPWCMLHR36IZJNNIQP:/var/lib/docker/overlay2/l/RKV YEXD2FH65FTMK76RDWPLESX:/var/lib/docker/overlay2/l/DX4JZRKTFP2GOO4V6 OWQ6CPJFY:/var/lib/docker/overlay2/l/6CYNWDKADUPPDZJ5IHOH2R7Y5S:/var /lib/docker/overlay2/l/JTPINUZIATXADL6XWFHG2OYGSF:/var/lib/docker/ov erlay2/l/OTSTIV5TTRHF4IUD7BODQ2FUON:/var/lib/docker/overlay2/l/QFNH3 EFS5EZGRTC4DPHU3PJ4TU:/var/lib/docker/overlay2/l/ZOOUKT2E5U4CSLP57Z7 MXYX5CD:/var/lib/docker/overlay2/l/3LUU6IDR2HWPTVBARC5K6XSMRC:/var/l ib/docker/overlay2/l/XOHYBP4RWXQKQZ43I7JKG24KE4:/var/lib/docker/over lay2/l/MN5M5B7AY5LPXQQC6V2MBJWWBF:/var/lib/docker/overlay2/l/3DRMKQ3 4AIZD2AROU3TVK3OCUT:/var/lib/docker/overlay2/l/73ZXDHBV6C53Q3SPXA57E OLGHU:/var/lib/docker/overlay2/l/C2IZBQ55EUTGEAAORSLE73ZPNM:/var/lib /docker/overlay2/l/ITHARNV7RPWN5S3BCZ2QDMZIMJ:/var/lib/docker/overla y2/l/TQKUV4LEG4AFUUCMFHHRLDBHAH:/var/lib/docker/overlay2/l/N75JZWPPD EKJ4DTN4GMEGTDIZL:/var/lib/docker/overlay2/l/QGUUYAETPMK643DG3AKWJAI IZA,upperdir=/var/lib/docker/overlay2/f23d2377a67b9ab1b49555ecd09b2c cdc037e0ee5d9e54f87e59f07f4398e71f/diff,workdir=/var/lib/docker/over lay2/f23d2377a67b9ab1b49555ecd09b2ccdc037e0ee5d9e54f87e59f07f4398e71 f/work 0 0 The crash occurs in the get_filesystem_nr() and read_filesystem() functions which call strchr(line, ' ') but fail to check if the result is not NULL. This patch adds this check, and when a single mtab entry requires more that one call to fgets() (i.e. the entry is longer than 512 bytes), it ignores outcome of the second and following calls. Bugs-Debian: https://bugs.debian.org/872926 Signed-off-by: Robert Luberda <[email protected]> Signed-off-by: Sebastien GODARD <[email protected]>
TL-Yao
pushed a commit
to scantist-ossops-m2/sysstat
that referenced
this issue
Apr 18, 2024
A segmentation fault may happen with "sadc -S DISK..." or "sadc -S XDISK..." when lines longer than 512 bytes are read from /etc/mtab. Such lines are possible for instance when overlay2 filesystem with docker is used. In such a case a single mtab entry can look like this (note that new line characters were added for readability, the original entry contained only one '\n' at the end): overlay /var/lib/docker/overlay2/f23d2377a67b9ab1b49555ecd09b2ccdc03 7e0ee5d9e54f87e59f07f4398e71f/merged overlay rw,relatime,lowerdir=/v ar/lib/docker/overlay2/l/L6VKIYXWBQSJ5R7V35SS43R6Y6:/var/lib/docker/ overlay2/l/UCCHKGXUJPWCMLHR36IZJNNIQP:/var/lib/docker/overlay2/l/RKV YEXD2FH65FTMK76RDWPLESX:/var/lib/docker/overlay2/l/DX4JZRKTFP2GOO4V6 OWQ6CPJFY:/var/lib/docker/overlay2/l/6CYNWDKADUPPDZJ5IHOH2R7Y5S:/var /lib/docker/overlay2/l/JTPINUZIATXADL6XWFHG2OYGSF:/var/lib/docker/ov erlay2/l/OTSTIV5TTRHF4IUD7BODQ2FUON:/var/lib/docker/overlay2/l/QFNH3 EFS5EZGRTC4DPHU3PJ4TU:/var/lib/docker/overlay2/l/ZOOUKT2E5U4CSLP57Z7 MXYX5CD:/var/lib/docker/overlay2/l/3LUU6IDR2HWPTVBARC5K6XSMRC:/var/l ib/docker/overlay2/l/XOHYBP4RWXQKQZ43I7JKG24KE4:/var/lib/docker/over lay2/l/MN5M5B7AY5LPXQQC6V2MBJWWBF:/var/lib/docker/overlay2/l/3DRMKQ3 4AIZD2AROU3TVK3OCUT:/var/lib/docker/overlay2/l/73ZXDHBV6C53Q3SPXA57E OLGHU:/var/lib/docker/overlay2/l/C2IZBQ55EUTGEAAORSLE73ZPNM:/var/lib /docker/overlay2/l/ITHARNV7RPWN5S3BCZ2QDMZIMJ:/var/lib/docker/overla y2/l/TQKUV4LEG4AFUUCMFHHRLDBHAH:/var/lib/docker/overlay2/l/N75JZWPPD EKJ4DTN4GMEGTDIZL:/var/lib/docker/overlay2/l/QGUUYAETPMK643DG3AKWJAI IZA,upperdir=/var/lib/docker/overlay2/f23d2377a67b9ab1b49555ecd09b2c cdc037e0ee5d9e54f87e59f07f4398e71f/diff,workdir=/var/lib/docker/over lay2/f23d2377a67b9ab1b49555ecd09b2ccdc037e0ee5d9e54f87e59f07f4398e71 f/work 0 0 The crash occurs in the get_filesystem_nr() and read_filesystem() functions which call strchr(line, ' ') but fail to check if the result is not NULL. This patch adds this check, and when a single mtab entry requires more that one call to fgets() (i.e. the entry is longer than 512 bytes), it ignores outcome of the second and following calls. Bugs-Debian: https://bugs.debian.org/872926 Signed-off-by: Robert Luberda <[email protected]> Signed-off-by: Sebastien GODARD <[email protected]>
TL-Yao
pushed a commit
to scantist-ossops-m2/sysstat
that referenced
this issue
Apr 18, 2024
A segmentation fault may happen with "sadc -S DISK..." or "sadc -S XDISK..." when lines longer than 512 bytes are read from /etc/mtab. Such lines are possible for instance when overlay2 filesystem with docker is used. In such a case a single mtab entry can look like this (note that new line characters were added for readability, the original entry contained only one '\n' at the end): overlay /var/lib/docker/overlay2/f23d2377a67b9ab1b49555ecd09b2ccdc03 7e0ee5d9e54f87e59f07f4398e71f/merged overlay rw,relatime,lowerdir=/v ar/lib/docker/overlay2/l/L6VKIYXWBQSJ5R7V35SS43R6Y6:/var/lib/docker/ overlay2/l/UCCHKGXUJPWCMLHR36IZJNNIQP:/var/lib/docker/overlay2/l/RKV YEXD2FH65FTMK76RDWPLESX:/var/lib/docker/overlay2/l/DX4JZRKTFP2GOO4V6 OWQ6CPJFY:/var/lib/docker/overlay2/l/6CYNWDKADUPPDZJ5IHOH2R7Y5S:/var /lib/docker/overlay2/l/JTPINUZIATXADL6XWFHG2OYGSF:/var/lib/docker/ov erlay2/l/OTSTIV5TTRHF4IUD7BODQ2FUON:/var/lib/docker/overlay2/l/QFNH3 EFS5EZGRTC4DPHU3PJ4TU:/var/lib/docker/overlay2/l/ZOOUKT2E5U4CSLP57Z7 MXYX5CD:/var/lib/docker/overlay2/l/3LUU6IDR2HWPTVBARC5K6XSMRC:/var/l ib/docker/overlay2/l/XOHYBP4RWXQKQZ43I7JKG24KE4:/var/lib/docker/over lay2/l/MN5M5B7AY5LPXQQC6V2MBJWWBF:/var/lib/docker/overlay2/l/3DRMKQ3 4AIZD2AROU3TVK3OCUT:/var/lib/docker/overlay2/l/73ZXDHBV6C53Q3SPXA57E OLGHU:/var/lib/docker/overlay2/l/C2IZBQ55EUTGEAAORSLE73ZPNM:/var/lib /docker/overlay2/l/ITHARNV7RPWN5S3BCZ2QDMZIMJ:/var/lib/docker/overla y2/l/TQKUV4LEG4AFUUCMFHHRLDBHAH:/var/lib/docker/overlay2/l/N75JZWPPD EKJ4DTN4GMEGTDIZL:/var/lib/docker/overlay2/l/QGUUYAETPMK643DG3AKWJAI IZA,upperdir=/var/lib/docker/overlay2/f23d2377a67b9ab1b49555ecd09b2c cdc037e0ee5d9e54f87e59f07f4398e71f/diff,workdir=/var/lib/docker/over lay2/f23d2377a67b9ab1b49555ecd09b2ccdc037e0ee5d9e54f87e59f07f4398e71 f/work 0 0 The crash occurs in the get_filesystem_nr() and read_filesystem() functions which call strchr(line, ' ') but fail to check if the result is not NULL. This patch adds this check, and when a single mtab entry requires more that one call to fgets() (i.e. the entry is longer than 512 bytes), it ignores outcome of the second and following calls. Bugs-Debian: https://bugs.debian.org/872926 Signed-off-by: Robert Luberda <[email protected]> Signed-off-by: Sebastien GODARD <[email protected]>
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Sebastien
I received https://bugs.debian.org/872926, whose reporter observed the following crash:
It turned out that this is related to use of the overlay2 filesystem with docker, which causes lines in /etc/mtab to be longer that 512 bytes (see the mtab.out file attached to the Debian bug.)
The crash occurs in the get_filesystem_nr() function which calls strchr(line, ' ') but fails to check if its result is not NULL.
I've just created a patch fix-mtab-reading-patch.txt that adds this check, and when a single mtab entry requires more that one call to fgets() (i.e. the entry is longer than 512 bytes), it ignores outcome of the second and following calls.
Regards,
robert
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