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kernel: syspread: avoid negative offsets in dir reads 

Should also fix CID 160109: Dereference after null check
This commit is contained in:
Giacomo Tesio 2017-08-14 18:39:45 +02:00
parent da588d69ec
commit 21b5682a43
1 changed files with 10 additions and 1 deletions
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11
sys/src/kern/port/sysfile.c
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@ -1,7 +1,7 @@
/* /*
* This file is part of Jehanne. * This file is part of Jehanne.
* *
* Copyright (C) 2015-2016 Giacomo Tesio <giacomo@tesio.it> * Copyright (C) 2015-2017 Giacomo Tesio <giacomo@tesio.it>
* *
* Jehanne is free software: you can redistribute it and/or modify * Jehanne is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by * it under the terms of the GNU General Public License as published by
@ -611,6 +611,7 @@ syspread(int fd, void *p, long n, int64_t off)
* the target device/server, but with a negative length * the target device/server, but with a negative length
* to read the buffer must be nil * to read the buffer must be nil
*/ */
InvalidAddress:
pprint("trap: invalid address %#p/%ld in pread pc=%#P\n", p, n, userpc(nil)); pprint("trap: invalid address %#p/%ld in pread pc=%#P\n", p, n, userpc(nil));
postnote(up, 1, "sys: bad address in pread", NDebug); postnote(up, 1, "sys: bad address in pread", NDebug);
error(Ebadarg); error(Ebadarg);
@ -641,6 +642,14 @@ syspread(int fd, void *p, long n, int64_t off)
sequential = 0; sequential = 0;
} }
if(c->qid.type & QTDIR){ if(c->qid.type & QTDIR){
if(p == nil){
/* With union mount we can't use negative
* offsets on directories as it's impossible
* to predict which fs support them and
* how they interpret them.
*/
goto InvalidAddress;
}
/* /*
* Directory read: * Directory read:
* rewind to the beginning of the file if necessary; * rewind to the beginning of the file if necessary;