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Overview
Comment: | On the first connection to a WAL-mode database that was not cleanly shut down and contains a left-over -shm file, truncate the -shm file to 3 bytes instead of to 0 bytes. Avoiding a truncation to 0 means that system monitoring tools can better detect if a process illegitimately tries to truncate a -shm file. Such a rogue process might think it is being helpful by cleaning up old files, but there is a race condition that can cause damage to the database. |
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SHA3-256: |
90cf32cde072a305f30c75a71665d1f9 |
User & Date: | drh 2018-10-11 13:51:48.266 |
Context
2018-10-11
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16:38 | Always reset the pager before changing the codec. (check-in: 0bf0fd242b user: drh tags: trunk) | |
13:57 | Merge enhancements from trunk. (check-in: 9e10d88bcb user: drh tags: apple-osx) | |
13:51 | On the first connection to a WAL-mode database that was not cleanly shut down and contains a left-over -shm file, truncate the -shm file to 3 bytes instead of to 0 bytes. Avoiding a truncation to 0 means that system monitoring tools can better detect if a process illegitimately tries to truncate a -shm file. Such a rogue process might think it is being helpful by cleaning up old files, but there is a race condition that can cause damage to the database. (check-in: 90cf32cde0 user: drh tags: trunk) | |
10:37 | In the CLI, fix a file descriptor leak following OOM and a missing va_end() call. (check-in: ec36d15a9e user: drh tags: trunk) | |
Changes
Changes to src/os_unix.c.
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4431 4432 4433 4434 4435 4436 4437 | rc = SQLITE_IOERR_LOCK; }else if( lock.l_type==F_UNLCK ){ if( pShmNode->isReadonly ){ pShmNode->isUnlocked = 1; rc = SQLITE_READONLY_CANTINIT; }else{ rc = unixShmSystemLock(pDbFd, F_WRLCK, UNIX_SHM_DMS, 1); | > > > > > | | 4431 4432 4433 4434 4435 4436 4437 4438 4439 4440 4441 4442 4443 4444 4445 4446 4447 4448 4449 4450 | rc = SQLITE_IOERR_LOCK; }else if( lock.l_type==F_UNLCK ){ if( pShmNode->isReadonly ){ pShmNode->isUnlocked = 1; rc = SQLITE_READONLY_CANTINIT; }else{ rc = unixShmSystemLock(pDbFd, F_WRLCK, UNIX_SHM_DMS, 1); /* The first connection to attach must truncate the -shm file. We ** truncate to 3 bytes (an arbitrary small number, less than the ** -shm header size) rather than 0 as a system debugging aid, to ** help detect if a -shm file truncation is legitimate or is the work ** or a rogue process. */ if( rc==SQLITE_OK && robust_ftruncate(pShmNode->hShm, 3) ){ rc = unixLogError(SQLITE_IOERR_SHMOPEN,"ftruncate",pShmNode->zFilename); } } }else if( lock.l_type==F_WRLCK ){ rc = SQLITE_BUSY; } |
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